The latest issue of Obesity offers both welcome rationality, important discussions and good chances of some decent hair pulling.
It features an editorial by Jean-Pierre Flatt from the Department of Biochemistry and Molecular Biology, University of Massachusetts.
Flatt gives us an insight into some important misconceptions about obesity. He even made us a list of contents:
1. Problems in applying the energy balance concept
2. Problems with the metabolic efficiency concept
3. The misleading emphasis on the importance of low resting metabolic rates
4. Misleading expectations about the importance of adaptive thermogenesis
5. Problem in judging the importance of de novo lipogenesis and of its metabolic cost
6. The irrelevance of the “nutrient partitioning” concept
7. Failure to recognize the greater impact of energy intake than energy expenditure
8. Difficulties in understanding food intake regulation
9. Conditions for body weight stability: settling point vs. set point
10. Problems with the application of the RQ/FQ concept
11. The “defense of body weight” concept
12. The different roles played by CHO and fat in energy metabolism
13. Food intake regulation and carbohydrate balance
14. The difficulty in obtaining experimental evidence about the role of carbohydrate balance in food intake regulation
15. The need to distinguish between the role of carbohydrate balance in food intake regulation and the role of habitual glycogen levels in body weight regulation
16. Understanding the recent increases in the preponderance of obesity
17. Why don’t people eat even more?
18. Confusion about the leverage of exercise on body weight
19. Is dietary fat or is dietary CHO the major culprit in causing weight gain?
20. How can inherited traits influence body weight regulation?
21. The leverage of inherited vs. noninherited factors
22. BMI vs. % ideal body weight
Lots of interesting stuff right? Right. There is lots of interesting food for thought in the editorial and much is welcome food. For instance the problems with the energy balance concept, and:
The use of settling point rather than set point:
This corresponds to a “settling point” (20). Such a view accommodates the fact that circumstances cause weight stability to occur for various degrees of adiposity. Thus it seems to fit reality much better than the concept of a «set point» or «ponderostat».
It has sometimes been considered that “set-points” are reset for different conditions, but in effect this argument reduces the set-point phenomenon to a settling point.
I agree with him that saying the body is «defending» itself against body weight change is not a very helpful thing to say:
The common tendency of individual body weights to return to their original value after a weight-changing intervention is often explained as the manifestation of a mechanism tending to “defend” a particular body composition. The problem with this concept is that it appears to imply that mechanisms exist to actively drive the fat mass to a particular level, much as one would expect if a set-point mechanism existed (21). It fails to take into consideration that before the intervention, body composition for a given individual had already evolved until a steady state of weight maintenance had become established.
He even mentions Mark Friedmans work on how liver substrate oxidation rates affect hunger, work I have previously written about on this blog.
But most of all, he talks about the importance of glycogen storage in obesity.
Thus, the role which increased habitual glycogen levels will play in promoting obesity in humans needs to be recognized!
And the dissonance?
After elaborating thoroughly on the importance of glycogen stores:
“In view of the considerations made above, it is not surprising that a high incidence of obesity is typically encountered in sedentary populations consuming diets providing substantial amounts of fat.” (my bold)
You can pull your hair now. It never seizes to surprise me how so much smart and something so incredibly stupid can be crammed into the same text.
Thus the answer to the question asked above is that the major culprit is the unrestricted and ubiquitous availability of a mixed diet, offering numerous appetizing foods, often in large portions, in which sugar, and to an even greater extent fat, contribute to raise the energy density.