Last week I posted about our collective belief, as a nation, that weight loss and maintenance is a problem solved by simple math - balance the "in" with the "out" columns of the calorie ledger and weight will be lost when the "out" exceeds the "in" and will be maintained when the two are equal.
Or so we're told.
I threw out the idea that weight isn't simply about math, but about chemistry.
The latest issue of the American Journal of Clinical Nutrition is out, and within is a very intriguing study where this very issue was central to the research conducted. It's one piece of the "weight is chemistry" equation, so let's take a look.
In the study, A novel interaction between dietary composition and insulin secretion: effects on weight gain in the Quebec Family Study, researchers followed subjects for six years to see what effect, if any, levels of insulin secretion had on weight.
The objective was to "determine whether physiologic differences in insulin secretion explain differences in weight gain among individuals consuming low- and high-fat diets."
This interest to investigate such was born from clinical trials where subjects consumed low-fat diets where results often revealed that there are huge variations between individuals consuming similar dietary ratios of macronutrients and reported calories; these differences are often chalked up to psychological and behavioral factors - motivation, compliance with diet, under-reporting of foods consumed, etc., ignoring the possibility that there is a physiological variation that may be at work.
In this study, the researchers noted the findings of Dansinger et al who compared four dietary approaches (Atkins, Ornish, LEARN and Zone), noting that "Of those assigned to the Ornish very-low-fat diet, mean weight loss was again small, 2 kg, but individual weight change ranged from almost –30 kg to >10 kg. This interindividual variation is commonly attributed to differences in motivation and compliance, but biological factors may also be contributory."
Thus the researchers in this study considered the the following for a test hypothesis: Low-fat diets are inherently high in carbohydrate because, for most people, the third major nutrient, protein, remains within a fairly narrow range. Carbohydrate has the most potent effect on insulin secretion of the major nutrients. Therefore, individuals with high insulin secretion consuming a low-fat diet might be especially susceptible to weight gain.
To investigate this, they "examined the associations between insulin concentration at 30 min (insulin-30) during an oral-glucose-tolerance test (OGTT) and change in body weight or waist circumference in the Quebec Family Study (QFS)" over a period of six years."
The findings were very interesting.
The primary findings of this study are that a proxy measure of insulin secretion strongly predicted weight gain and change in waist circumference over 6 y in adult whites, especially among those consuming lower-fat diets.
...our results and those involving GI suggest the existence of a unique physiologic phenotype that responds poorly to high insulin-stimulating diets, regardless of whether these diets are high in carbohydrate or have a high GI. Moreover, the combination of a high-carbohydrate and high-GI diet—that is, a diet high in glycemic load (GL)—may produce especially great weight gain among individuals with this phenotype.
While the researchers reached the conclusion that these findings suggest there exists a "unique physiological phenotype that responds poorly to high insulin-stimulating diets" - such assumes we're supposed to consume a low-fat, high carbohydrate diet; if we're not responding well to such a diet, it's because some have a unique physiological phenotype rather than consuming a diet that is at odds with human physiology.
I'd counter that it's just as likely it has nothing to do with a "unique phenotype" among us, but rather the expected results of a modern diet at odds with our physiology. Minor quibble.
Nonetheless, the finding is important as it points directly to individual metabolic factors playing a role within the context of the diet - low fat verus high fat - not just calories. In this study, it was insulin secretion. It mattered, especially in those consuming a low-fat diet.