low fat diet – Pål Jåbekk

Diet, weight loss and body composition changes

This is an unfortunately long post, and I apologize for it, but the reason is that I find all this so darn interesting. Hope you do to.

A little while back I looked closer at some of the science behind diet, weight loss and body re-composition. I have heard people say on several occasions that a low carbohydrate diet will prevent loss of muscle mass and that all weight lost is fat. So I wanted to find out once and for all what really happens with our body when we lose weight. I’ll show you some of the data, and although these studies are not the only ones, I am confident that the studies presented here give a satisfactory accurateness

So there is much debate about what happens to our body composition when we lose weight and perhaps especially when we do it using a low carbohydrate diet. This quote is from Sachiko T. et al 2001. Dietary Protein and Weight Reduction: A Statement for Healthcare Professionals From the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association:

“Some popular high-protein/low-carbohydrate diets limit carbohydrates to 10 to 20 g/d, which is one fifth of the minimum 100 g/d that is necessary to prevent loss of lean muscle tissue.”

Clearly the AHA suggests that we will lose muscle tissue by going low carb. In my school we used the exercise physiology textbook from McArdle, Katch and Katch (2007) which said this:

”…low carbohydrate diet sets the stage for a significant loss of lean tissue as the body recruits amino acids from muscle to maintain blood glucose via gluconeogenesis.”

Once again, low carbohydrate dieting does not seem a good idea if we want to preserve muscle mass while we lose fat mass.

But the questions remains unanswered; how much muscle mass do we lose if we go low carb and can we do anything to prevent a potential loss of muscle tissue?

Let us look at some studies and see what they tell us.

Studies
This study from Bonnie Brehm and coworkers compared a low carbohydrate diet to a low fat diet:

All participants in the above study were women and they were obese. Dietary energy content was reduced in both diets and body composition was measured using Dual Energy X-ray Absorptiometry (DEXA). As you can see, weight loss was greater with low carb, but so was loss of lean body mass (LBM) and the percentage loss of LBM was not much different between diets.

Here’s another study:

This was a crossover study where all the participants tried two different diets in random order. The results are given under:

As is usually the case in weight loss trials, the men lost more weight than the women. And once again low carb caused a greater weight loss, but also quite the loss of lean body mass. The women eating low fat seemed to lose the greatest percentage LBM, which is also a recurrent theme in weight loss trials.

Next, here’s Kelly Meckling and coworkers:

One of the goals in this study was for the low fat group to reduce their calorie intake to the naturally reduced level of the low carbers. Weight loss did not differ between groups, but loss of LBM was significantly larger in the low carb group and over 25% of the LC weight loss was lean body mass. Body composition was measured using bioelectrical impedance analysis (BIA).

Next, as study from William Yancy and coworkers from 2004:

Weight loss with low carb was double that of low fat and this time loss of fat free mass (FFM) was actually quite larger in the low fat group. LBM is what is left if we remove fat mass and skeletal mass. Fat free mass is, not surprisingly, total mass minus fat mass. LBM and FFM are used interchangeably.

It seems that loss of non-fat mass is common, regardless of diet, but we need to look at some more studies to get a clearer picture.

Here’s one from down under, from Manny Noakes:

This is a short study, but with 83 participants. The results are pretty similar, both when it comes to weight and LBM loss, but in both diets around 30% of the lost weight was LBM and that is rather much.

Another one from Australia. Here’s Jennifer Keogh and coworkers:

Both diets were 30% energy restricted and designed to be isocaloric. Once again there was a significant loss of fat free mass with both diet strategies.

Jeff Volek brought us this study in 2008:

An Atkins type diet was compared to a regular calorie restricted low fat diet in 40 men and women. Weight loss was greater with low carb, but so was loss of LBM. So far, there seems to be little truth to any claim that low carb preserves LBM.

This next one is another crossover study:

Alexandra Johnstone and coworkers showed us yet again that weight loss is greater with low carb, but that so is loss of FFM. Notice that this is a study of men only and so the percentage loss of FFM is much smaller than in studies of women.

One last study. Third one from Australia, this time by Grant D. Brinkworth:

118 people participated in this eight week study and were scanned with DEXA. Weight loss was greater with low carb and both groups lost about 20% FFM.

To summarize, loss of fat mass is greater with LC than LF diets. Loss of LBM is common on both LF and LC diets, but as we will see, not obligate. But there are some considerations to make first.

Considerations

First of all, any loss of water will usually be considered LBM and so if there is a difference in water loss between diets, this will affect loss of LBM/FFM. Carbohydrate restriction usually does cause a greater loss of body water, at least in the initial phase of the diet. Loss of glycogen with low carb will cause a parallel loss of water and so there is reason to expect a larger loss of LBM with low carb, and we need to remember that LBM is not a measure of muscle proteins.

Contradictory findings

Although loss of LBM is clearly common on low carb diets, there are studies suggesting that such a loss can be avoided.

In a very small crossover study by Benoit et al from 1965 we can see the obvious advantage of low carb dieting compared to fasting:

Notice the difference in LBM loss. One likely advantage of carbohydrate restriction is that the combination of adequate protein intake and high ketone body production spares muscle proteins from being used to produce glucose. The Benoit study is small, but it suggests that loss of LBM is not a necessary consequence of low carb dieting.

And look at this one:

In this study of twelve men, LBM increased during the diet period, even though there was no change in the exercise pattern of the subjects. It is results like these, which sometimes appear, that suggests that it is possible to lose weight in a way that spares muscle tissue. In another very small study of very obese adolescents, similar results were found:

After eight weeks of a very low calorie ketogenic diet, lean body mass increased by almost 1,5kg while 15kg of fat was lost.

So I think it’s time to ask what the difference between these few studies where LBM increases (in spite of water loss) and the RCT’s where a low carbohydrate diet always leads to some LBM loss. But remember also that not all LBM is functional LBM. That is, we expect some loss of LBM and some LBM can be lost without negative consequences. We must remember to keep our feet on the ground, there is no problem with some loss of LBM with large losses of fat mass.

To make a long story short, there are some important factors we can manipulate in order to reduce loss of LBM. Being a man is perhaps the most effective. Men lose more fat and less LBM when they lose weight. It’s just the way it is. But both men and women can increase their protein intake. In many of the RCT’s in this post, average protein intake was low, often around 1g/kg body weight/day. The optimal intake is probably closer to 1.8g/kg/day (severely overweight people should use ideal body weight instead of actual body weight).

Several studies have found a correlation between protein intake and LBM loss. James Krieger wrote this in 2006:

And he concluded thusly:

In a very recent review article, Stuart Philips and Luc van Loon has this to say:

The thing with carbohydrate restriction is that is causes a greater fat loss and greater LBM loss than low fat strategies, but the end result is that low carb thus causes a greater reduction in body fat percentage and so the greater change in body composition. To optimize the results, protein intake should most likely be kept at >1,5g/kg/day. Here’s another quote from Phillips and van Loon:

There is also the matter of sodium and potassium that might play a part in the results. Potassium is an important intracellular ion in our muscles and adequate potassium is important for creating an anabolic environment. The trouble with ketosis or severe carbohydrate restriction is that it causes our kidneys to excrete sodium and unless that sodium is properly replaced the kidneys compensate by excreting potassium. In short, when optimal body composition changes is the goal, or optimal performance, salt intake is important and should be a good deal higher than the daily recommended intake.

In addition to minding our protein and salt intake, we can of course also do resistance exercise in order to increase lean mass retention or even increase lean mass while reducing fat mass. It is, not surprisingly, well documented that resistance exercise, as a part of weight loss, is very effective at reducing lean mass loss, regardless of diet. But in order for resistance exercise to yield optimal results, protein and salt intake must be optimized.

Richard Wood and coworkers just published results from a study where overweight older men were put on two different diets with or without resistance exercise. Here are the results:

Even though the results favor both low carbohydrate dieting and resistance exercise, I must say that I was surprised at the amount of FFM loss in the low carbohydrate and resistance exercise group, even when considering that some is water loss. After 12 weeks I would have suspected FFM to have increased. But there are once again some factors to consider. First of all, the mean age of the participants were 60 years. This may have caused the results to be smaller than if younger men participated. Also the resistance exercise was not very heavy, it could have been a good deal heavier and it is likely that muscle hypertrophy would then have been greater.

Donald K. Layman and coworkers compared the effects of two different diets varying in protein and carbohydrate content, with or without resistance exercise. The graphs on the left are women and the ones on the right are men:

Clearly, both increasing protein/decreasing carbohydrate and resistance exercise improve body composition changes. The low carbohydrate diet in this study was not very low. Average carb intake during the intervention was 141g in LC and 126g in LC+RE. Protein intake was 110g and 102g respectively.

I’d like to compare the results of a study I conducted in 2010 with that of a study from Donnely from 1991:

These are two very different strategies. In our study the participant were told to be in dietary ketosis, but could eat as much as they liked. In Donnely’s study calories was severely restricted. Also in our study the participants exercised twice a week, whereas in Donnely’s they exercised four times per week (resistance exercise). They are both effective strategies both for losing weight and changing body composition, so it is up to us what we prefer. I for one would like to eat as much as I please and not have to exercise that much to get the results I want.

The conclusion
Loss of LBM with weight loss is common but not obligate. A low carbohydrate diet is no grantee for all weigh loss being fat. In order to achieve optimal body re-composition one should reduce carbohydrates, make sure to eat enough protein and salt, and do regular heavy resistance exercise. The results one can achieve are quite astonishing.

Low fat – we’re gonna need more nails

Low fat dieting for weight loss doesn’t work. That is, it works, just very very poorly. In fact it works just enough for confused obesity researchers to call the weight loss significant. Somewhere along the way, it was decided that a 5% loss of initial body weight is to be considered clinically significant [1]. So if you weigh 100kg and work your butt of (which is what you are not really doing) to get rid of 5kg, scientifically speaking that’s a success. When Bray, Bouchard and James wrote the Handbook of Obesity [2] they presented pretty compelling evidence that traditional weight loss does not work. They still continued recommending low fat for weight loss. The 2002 Cochrane meta-analysis titled “Advice on low-fat diets for obesity” by Pirozzo and coworkers [3] was recently withdrawn. The Cochrane organization claims the conclusions are out of date. What the metaanalysis showd was that

“…fat-restricted diets are no better than calorie restricted diets in achieving long term weight loss in overweight or obese people.“

And the authors concluded that both strategies produced a weight loss that was

“…so small as to be clinically insignificant.”

This conclusion was reached by looking at the best studies available up till 2002. No new studies have provided evidence the conclusion of the meta-analysis was wrong, but it seems the Cochrane Collaboration could not live with such a politically incorrect conclusion.

In a new study, and a pretty damn large one at that, the researchers went out of their way to resurrect the dead, but sadly not buried lowfatforweightlossworksgoddamnit-hypothesis.

Enter the Look AHEAD Study. The study was a “…multicenter randomized clinical trial to examine the effects of a lifestyle intervention designed to achieve and maintain weight loss over the long term through decreased caloric intake and exercise.”

Here’s how the authors view the study:

“As perhaps the most extensive test of long-term multidisciplinary lifestyle intervention to date, the Look AHEAD (Action for Health in Diabetes) trial presents a unique opportunity to examine the long term viability of lifestyle intervention as a clinical and public health strategy for obesity and type 2 DM.”

A total of 5,145 overweight/obese men and women with type 2 diabetes were randomly assigned to an intensive lifestyle intervention (ILI) or a usual care group, referred to as Diabetes Support and Education (DSE).

“The ILI included diet modification and physical activity and was designed to induce at least a 7% weight loss at year 1 and to maintain this weight loss in subsequent years. The ILI participants were assigned a calorie goal (1200- 1800 kcal/d based on initial weight), with less than 30% of total calories from fat (<10% from saturated fat) and a minimum of 15% of total calories from protein.”

“The exercise goal was at least 175 minutes of physical activity per week, using activities similar in intensity to brisk walking. Behavioral strategies, including self monitoring, goal setting, and problem solving, were stressed. The ILI participants were seen weekly for the first 6 months and 3 times per month for the next 6 months, with a combination of group and individual contacts. During years 2 through 4, participants were seen individually at least once a month, contacted another time each month by telephone or e-mail, and offered a variety of ancillary group classes. At each session, participants were weighed, self-monitoring records were reviewed, and a new lesson was presented, following a standardized treatment protocol.”

Bet you wonder what kind of marvelous results you can get from this intensive intervention. Bet you think all the participants in the ILI group came out of the study looking like Greek gods. I mean, 4 years of exercise, diet and pampering…

At the end of the 4 year period the participants in the ILI group, whose average baseline weight was 95kg in women and 109kg in men, reduced their weight by 4.7%. Actual weight loss was 4,9kg.

Here’s nice graph from the study

This figure shows how 74% of the participants in the ILI group lost weight while 26% gained weight. Only 46% of the group lost more than 5% body weight:

So there you have it. These are the grand effects of 4 years of intensive lifestyle changes. I’m not impressed.

PS.

Funny thing. If you read the abstracts, the article in which the main results were published [4] states that the average weight loss was 6,15%, yet in a more recent article addressing what factors correlated with long term success, the number is 4,7% [5]. It turns out that the number 6,15% is an average of the weight lost at 1, 2, 3 and 4 years which is not a very nice way to present data. I would say it’s a pretty poor way to present data. You have to read the entire article to find that “…the ILI group maintained a mean weight loss of 4.7% at year 4.”

Literature

1. J. Stevens et al., «The Definition of Weight Maintenance,» Int J.Obes.(Lond) 30, no. 3 (2006): 391-399.

2. George A. Bray, Claude Bouchard, and W. P. T. James, Handbook of obesity, ed. George A. Bray, Claude Bouchard, and W. P. T. James. (New York: M. Dekker, 1997), xii, 1012.

3. S. Pirozzo et al., «Advice on Low-Fat Diets for Obesity,» Cochrane.Database.Syst.Rev., no. 2 (2002): CD003640.

4. R. R. Wing, «Long-Term Effects of a Lifestyle Intervention on Weight and Cardiovascular Risk Factors in Individuals With Type 2 Diabetes Mellitus: Four-Year Results of the Look AHEAD Trial,» Arch.Intern.Med. 170, no. 17 (2010): 1566-1575.

5. T. A. Wadden et al., «Four-Year Weight Losses in the Look AHEAD Study: Factors Associated With Long-Term Success,» Obesity.(Silver.Spring) 19, no. 10 (2011): 1987-1998.

Fat people are liars

Obviously! Obesity is a remarkably simple problem to solve. Eat less and move more. When energy expenditure exceeds energy intake, you lose weight. Many people claim to have tried eating less and exercising more and claim that it does not work. As this would be a violation of the laws of thermodynamics it is quite unlikely.

Not only do overweight people claim to break the fundamental laws of nature they also constantly lie about how much they actually eat.

Elaine Prewitt and coworkers examined the effect of a 37%-fat (HF) diet for 4 weeks followed by a 20%-fat diet (LF) for 20 weeks on body composition and weight in 18 premenopausal women with body mass index (BMI) of 18-44. They found that

Despite adjustments in energy intake to maintain weight throughout the study, by the end of the LF period, energy intake had increased significantly in comparison with the HF diet (119% of the HF intake, P < 0.0001).

The authors knew what kind of people they were dealing with and wrote

We have no means of assessing the degree of food waste by subjects when meals were taken out but there was no reason to attribute the magnitude of energy increase we observed to overreporting of dietary infractions. By contrast, one would expect the subjects, particularly obese subjects, to underreport extra foods eaten.

W. Daniel Schmidt and coworkers exercised overweight women. All study groups were put on an energy restricted diet. The control group only dieted without changing exercise routines, but somehow they didn’t lose any weight. The authors write:

The fact that the control subjects in our study did not lose weight is perplexing and conflicts with other research that generally supports weight loss with caloric restriction [17, 18]. One explanation may be that subjects simply underreported the amount of calories consumed, thus making this an issue of noncompliance.

Not only are fat people liars, but fat people on low fat diets are the worst. James Krieger, everyone’s favorite researcher, suggests that:

…subjects on low-fat diets systematically underreport energy intake compared with subjects on low carbohydrate diets.

In support of his theory he cites a study where weight loss from a low fat diet did not turn out as predicted.

Fat people on low fat diets are not only the worst liars around, they are also not very smart. Kelly A. Meckling and coworkers compared a low fat diet to a low carbohydrate diet in overweight men and women. They write:

Energy restriction alone predicted a weight loss of 5.5. and 6.9 kg, respectively, in the LF and LC groups, which was close to the observed values of 6.8 and 7 kg for the same groups. Slight differences, particularly for LF subjects might be explained by underreporting of habitual diets, as the subjects became better able to estimate their intakes and keep better food records as the trial proceeded.

Those put i a low carb group obviously nailed the food reporting task right away, even before they actually were put on the diet, and missed the predicted weight loss by a mere 100 grams.

Everyone knows low fat fatties are the worst. Thermodynamics applied to food and the body is very simple, yet predicted weight loss are often not achieved by low fat fatties.

Writes Jennifer B Keogh and colleagues (when a low carb group lost more weight than a low fat group in their study):

Greater weight loss with a low-carbohydrate diet than with a conventional low-fat diet has been reported previously (2– 4, 57). Subjects in these studies reported similar energy intakes despite differences in weight loss, which suggests that the conventional diet group underreported their intake (3, 4, 57).

A group of Dutch researchers set out to test the extent of underreporting in 30 obese men. Their conclusion:

Total underreporting by the obese men was explained by underrecording and undereating. The obese men selectively underreported fat intake.

Not only did these men lie about how much they were eating, they didn’t even eat as much as they should have. They underrate. Those bastards!

If by chance you are wondering if the methods of the Dutch researchers were bulletproof, they weren’t. Still…

It is possible that overweight people under report more than lean people. But people seem to think that the under reporting somehow is the reason they are fat. They don’t know how much they eat and so they stuff themselves and grow fat. It is also possible that low fat diets does not work very well and that the human body is more metabolically complex than the simple energy calculations used predict.

But if overweight people do really under report more than «normal» weight people, are they then fat because they under report and lie, or are they perhaps under reporting because they are fat and afraid of being stigmatized as gluttonous and desperately trying to keep some of their dignity?

The death of a theory

«If I haven’t seen further than others it’s because giants were standing on my shoulders« – Richard Feinman quoting Hal Abelson quoting his roommate.

I’ve been reading a fantastic book lately. Lee Smolins “The trouble with physics – The Rise of String Theory, the Fall of a Science, and What Comes Next.” The book is exactly as great as the title sounds, although admittedly, I only understand a fraction of it. Lee Smolin discusses string theory, how is came to be the leading theory in theoretical physics and how it might prove to be one of the greatest dead ends in the history of science. I’m by no means qualified to discuss theoretical physics, but as always when reading science my head draws parallels to my own area of research. String theory, as the leading theory in theoretical physics, does have a lot in common with the leading theory in obesity treatment, the low fat theory.

There is little doubt that the “low fat diet for weight loss” theory is a theory that should have been rejected a long time ago. There are good reasons it should be rejected. It only indirectly addresses the physiological causes of excess fat storage. And because it only indirectly addresses the real problem, it only works temporarily.

«They will devise numerous articulations and ad hoc modifications of their theory in order to eliminate any apparent conflict.» – T. Kuhn

In the near future the low fat theory might be considered one of the greatest blunders in health science. At least, it has the potential to be considered as such. Some theories have been shown to be near immortal and this is definitely one of them.

It is easy to draw parallels between the low fat theory and string theory. String theory is an attempt to unite different aspects of physics, general relativity and quantum mechanics, into one great unifying theory, a complete theory of nature. It is based on simplicity and beauty, but what seems intuitively logic is not necessarily logic at all.

Before Keppler, the planetary orbits were thought to be circular. A circle is beautiful and symmetric and it seemed logic that this was how the planets moved. And yet, observations showed the planetary orbits to be elliptical. The low fat theory is also intuitively logic. Fat contains much more energy than other nutrients of the same weight and excess energy is stored as fat. Thus eating fat in excess makes the body store fat in excess. Fat from foods makes fat in the body. It is simple, beautiful, logic and wrong.

String theory, like the low fat theory, does not have a good track record as far as theories go. It started as a simple theory, and many people think that a theory that incorporates all of physics should be simple. But there were fundamental problems with string theory right from the start. In order to get it to work on paper a lot of dimensions had to be added (the 3 dimensions we are used to, were by far enough), new and unobserved particles were invented and the theory had to be background dependent to work when the whole point was that it should be background independent. It also made few predictions and proved close to impossible to falsify by experiment. A theory has to be falsifiable, because only by opposing repeated attempts of falsification does a theory evolve into truth.

«A nice adaptation of conditions will make almost any hypothesis agree with the phenomena. This will please the imagination, but does not advance our knowledge.» – J. Black

Still, string theory survived. It survived because it was constantly added ad hoc additions and because conditions were constantly changed. Now, this is a normal scientific process. Few theories are perfect when they emerge. The question is, how many conditions can be changed and alterations be made before the theory should be replaced by a new one?

Like the string theory, the low fat theory needs to rest on several assumptions in order to survive. The low fat theory is based on the belief that energy intake and energy expenditure are independent factors. Little scientific data support this, and it is not possible to consider the body to be a closed system. It is also based on the assumption that we can all control our energy intake and expenditure by will. Low fat diets don’t work in the long run. Upon discovering this we can change the theory or consider it faulty. Because it didn’t work, modifications were made; People are lazy, have poor self control, exercise too little and so on. None of these assumptions are justified. They are often not given directly, but disguised by the fact that they are logical consequences of the theory.

Both the low fat and string theory were the leading theories in their field for a long time and in many ways still are. Other theories, even better theories, has constantly been placed in the shadow and were given little financial support. People who worked on alternative theories to string theory were automatically outsiders, low in the field’s hierarchy, just like the researchers working on low carb diets was given less attention than they deserved.

”This is painful for many who have invested years and even decades of their working lives in string theory. If it is painful for me, imagine how some of my friends who have staked their whole careers on string theory must feel. Still, even if it hurts like hell, acknowledging the reduction ad absurdum seems a rational and honest response to the situation. It is a response that few people I know have chosen. But it is not one that most string theorists choose.” – Lee Smolin

Although there’s still some hope for string theory, there is none for the low fat theory. We’ve tried it. It didn’t work. We are getting fatter than ever. Often the scientific standards themselves are reduced in order to keep these gargantuan theories alive. Intentionally or not, the result of this is sometimes the death of science itself and the people considered scientists are no longer scientists in the true definition of the word. The death of a theory is replaced by the death of science.

It doesn’t take an expert
There are usually no sides in science. Sometimes people ask me; what do you believe in/ who do you believe to be right or what dietary method do you teach? The way I see it the only correct answer is that I don’t believe anything. I know what some of the facts are. I can make some calculated guesses on what is less certain, and there is a lot I don’t know. Of course, I cannot actually give this answer. People need substance, and as soon as I mention carbohydrates, I’m on the low carb side. But there are no sides. Science is not a battle between teams, it is a unified search for truth.

“The reason that mathematics invented the idea of proof and made it the criterion for belief is that human intuition has so often proved faulty” – Lee Smolin

Basic scientific principles are not difficult to understand and they are independent of scientific subject. When scientific standards are reduced, any lay person can see the faulty logic. Tom Naughton is being accused of writing about things he does not have the authority to write about. But, he does know what he is talking about, much more so than many of the experts in the field. You do not have to be a nutritionist or even a scientist to address the core problems related to basic scientific principles. A beginners mind easily spots the obvious flaws. Diabetes means you can’t handle dietary carbohydrates, yet a doctor may easily tell you to cut fat from your diet after diagnosing you. The doctor’s mind is that of an expert, clouded by experience.

«…insist that we should change the rules of science just to save a theory that has failed to fulfill the expectations we originally had for it.” – Lee Smolin

Why aren’t we all fat?

I have noticed that there is one argument used in the nutrition debate that is used by both the low carb and the low fat community (in this context, dividing it into two sides make perfect sense). The same argument keep flying back and forth but I feel it is rarely given the response it deserves.

It goes something like this; “If carbohydrates make us fat, why aren’t all the people of the world, like many Asian people, who live on high rice diets, fat?”

For the record, I am fully aware that the composition of a traditional Asian diets is debated and that a general shortage of food may protect against any harmful effects of a high carb diet. The above argument is a poor argument for another more important reason.

In the low carb world the same argument is used, often in a form resembling the following; “Eating fat cannot make us fat. Because, if fat made us fat, why aren’t all people who live on regular high fat diets, like the Inuit or the Masai fat?”

This argument (and all similar) is easily refuted. Part of the reason these arguments are fallacious is that they rely on an unstated assumption, an assumption we cannot make. A causal factor may affect us differently and may only end up in full blown disease in predisposed individuals. We are not genetic copies. If we were all clones, finding causal factors would be so much easier (there is a reason twins make for popular study subjects). But we’re not. We respond differently to the same stimuli and only by being clones would we all be able to react similarly.

Smokers have a greatly increased risk of lung cancer, yet many smokers smoke their way through long lives with no cancer.

Still, the causal factor is still the causal factor. Insulin and glucose drive fat storage in all of us. Some of us however have counter regulatory mechanisms that may overpower the fat storing effects causing us to remain lean. The above arguments rest on the assumption that we are genetic copies. We’re not.

Ok, I realize the clone analogy is stretching it a bit. After all, as members of the same species we are very similar and we may easily all respond similarly to the same stimuli. But the truth is that the arguments do rest on the assumption that we will respond in the same way and the danger is that the assumption will be used to discard a theory when responses differ.

In some studies of low carb diets the results have been less than expected. My experience is that many of these studies are also easily criticized, but that doesn’t really matter. It also doesn’t matter that studies using body weight may not detect large alterations in body composition. What matters is that the cause for a disease does not necessarily make everybody exposed to the causative agent, sick. Carbohydrates may easily be the main cause of excess fat accumulation in fat cells even if not everybody who eats great amounts of carbs gets fat. We cannot simply reject a theory that points to carbohydrates as the main cause of overweight just because there are people who don’t get fat in the face of plentiful carbohydrates.

«If any and every failure to fit were ground for theory rejection, all theories ought to be rejected at all times.» – T. Kuhn

Imagine a disease spreading through society and everything points to a virus as a cause. Then some people argument that the virus cannot be the cause of the disease, simply because there are people being exposed that does not get sick. It makes no sense.

On a similar note, the fact that you can lose weight by starving yourself (eating less energy) does not in any way contradict a theory pointing to carbohydrate as the causative agent.

The simple and undeniable fact is that many high quality studies of low carb diets have illustrated the diets efficiency in reducing weight. It makes perfect physiological sense and even evolutionary perspectives support it. These results cannot be rejected simply because someone loses weight by eating less energy. The results still stand. Getting them to fit with results from energy restriction studies is a matter of physiology, not theoretical science.

So, although carbohydrate restriction does not always give the expected positive results, this is not ground for theory rejection. On the other hand, when low fat diets have never given the long term results the theory predicts, this is ground for rejection. Treating overweigh people with low fat diets is a prime example of treating a symptom, the fat stores, rather than treating the cause of the fat storage. Because this is a strategy focusing on a symptom is will not work long term. Science supports this. Low fat diets simply do not work long term. We must reject the theory and try something else.

“Is there a chance that such observations have already been made but ignored because, if confirmed, they would be inconvenient for our theorizing?” – Lee Smolin

Intention to treat – what was the question again?

If you haven’t already heard there is a new low carb study out. It shows similar effects on weight compared to a low fat diet over 2 years, but better HDL results in the low carb arm. It’s a really interesting study, but I’ll leave it to others, like Jimmy to elaborate.

Once again this low carb study is from Gary Foster and colleagues. Foster has previously given us this one. Although containing a lot of interesting data the researchers once again insist on only presenting the data as intention to treat with missing data carried forward.

Statistics is definitely not my strong side, and if I’m way off on this one please show me why. And if there is a stat wiz out there who can tell me why this is the right way to present results, please do.

The researchers did do some sort of sensitivity analysis and tried to justify using the entire sample of 307 participants in the final analysis. But it still does not compare to actually giving us the data on the compliers vs. non compliers. A lot of people dropped out of the study. Of the 154 randomized to the low fat group, 49 was not assessed at 24 months. Of the 153 in the low carb group, 64 were not assessed at 24 months.

Now, intent to treat analysis is a perfectly fair method to use. But it means that the results cannot tell us which dietary approach is the more effective. If we want to know which diet causes the greatest weight loss we must look at the data from the participants that actually followed the diet, and only those. What the results of this recent study tells us, is the effect of being put on a diet as opposed to the effect of following one. Is it really so bloody impossible to include data on compliers vs non compliers? As interesting as it is to know the effect of being put on a diet I for one would also like to know the actual effect of following the diets.

Like many other studies using similar analyses, this one also show a regression to the mean, that is the results differ the most at 6 months and slowly merge into similarity as the low carbers eat more carbs, and the low fat group eat more total energy. Whether this is because of the type of analysis and the increasing number of participants discontinuing the treatment is beyond me.

The title of table 2 of the study says is all really, “Predicted Mean Changes…”. But what about the actual change and the actual effect of following the prescribed diet?

Richard Feinman has written this article, illustrating the trouble with using an intent to treat analysis.

Still, Foster has done a good job and provided interesting data. Looking forward to seeing how this study is going to be received.