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By Team ICG® Master Trainer Joan Kent

A while ago, based on some long-held suspicions, I ran a PubMed search on weight gain and weight loss to assess the accuracy of a widely held belief.  The belief, as the above title suggests, is that weight management hinges on the so-called “simple arithmetic” of calories in and calories out.

Even with the limited time I had for the search, I still located approximately 35-40 articles in various science journals that seem to challenge the calorie theory.  I”™ve categorized the results below, but need to start with a caveat.  Most of the studies cited in this post were done on animals.  (I”™ve indicated specifically when the subjects were human.)

Some people will object because of that.  For their benefit, I”™d like to make two points:  1) Studies of this type would be unethical to perform on human subjects.  No review board anywhere would approve research that involves locking people in a room, taking all control of their food intake away from them, and forcing them to gain or lose weight.  2) Are you truly prepared to state that weight management centers on calories in/calories out in the human body, while it”™s Anything Goes with animals?  Knowledgeable veterinarians, for example, have confirmed that the metabolic effects of Cushing”™s disease, including the role of hormones in weight gain, are identical in humans and dogs.

So what happened in the studies?  To sum it up, dietary factors were found to disrupt the link between calorie intake and weight, and different nutrients and hormones affected the weight outcome.

Fat content of the diet affected weight gain and loss.

- Rats on high-fat diets developed severe obesity without overconsumption of calories (4 studies).

- Mice showed greater weight gained per calories consumed (called “feeding efficiency”) on high-fat versus low-fat diets (1 study).

- Calorie-restricted, isocaloric diets of 10% and 50% fat both reduced body weight in rats, but body fat was higher in the 50% group (1 study).

- Total fat intake, rather than calorie intake, correlated with weight gain and was due principally to the saturated fat component (1 study).

- Saturated fat is associated with greater weight gain than unsaturated fat (2 studies).  [This makes no sense from a calorie standpoint, since all fats contains 9 calories per gram.  But saturated and unsaturated fats affect hormones differently, as mentioned briefly in a previous ICG® post on Cholesterol.]

- Fecal analysis showed people who consume nuts regularly excrete more fat, suggesting a discrepancy in gross calorie intake and calories absorbed (1 study).

Sugar content of the diet affected weight gain and loss.

- Abdominal fat deposits were caused by high-sucrose, isocaloric diets in rats, although the rats showed no differences in weight gain when compared with controls (1 study).

- Rats fed sucrose plus standard chow did not eat more calories than controls, but gained significantly more weight per calorie consumed (feeding efficiency) and had higher body fat than controls (1 study).

- Severe obesity developed in rats on a high-sugar diet and in rats on a high-fat diet, although controls eating standard chow ate significantly more calories than either the sugar group or the fat group (1 study).

- In a study of human identical twins, the dietary factor isolated as causing a difference in BMI between twins was sugar intake (1 study).

Nutrients affected sugar-induced weight gain.

- The protein content of a high-sucrose diet was inversely related to the effects of sucrose on weight gain and feeding efficiency (1 study).  [Protein triggers the release of glucagon; its effects oppose those of insulin.  More on insulin below.]

- Minerals added to a standard chow-plus-sucrose diet did not change calories, but decreased weight gain and feeding efficiency and improved glucose tolerance (1 study).

Insulin, a “fat storage” hormone, is a factor in weight gain.

- Rats injected with insulin gain weight with no change in diet or calorie intake (standard textbooks).

- Diet-induced insulin resistance preceded obesity development in rats (1 study).

- Insulin resistance functions as an adaptive mechanism to prevent further weight gain in obese human subjects (3 studies).

- A good night”™s sleep vs. restless sleep altered hormone balance.  Restless sleep caused fat storage to increase (2 studies). ”¨”¨ [This result seems contradictory in light of calorie balance:  Wouldn”™t tossing and turning all night burn more calories than sleeping soundly?]

- The 24-hour rate of fat oxidation by skeletal muscle may be determined either by genetics or by diet.  Insulin-triggering foods lower it (2 studies).

- High fructose intake induces high insulin levels, which can cause weight gain (5 studies).

- Chronic stress increases insulin and decreases brain dopamine, norepinephrine and beta-endorphin.  The changes shift food preferences to carbs (specifically sugar) and fats, leading to weight gain (9 studies).

What appears to be a balance of calories in/calories out is often the result of a change in diet composition.  That, in turn, changes the hormonal response.  Hormones can affect weight more profoundly than calories.  (More about hormones in a future post.)

Despite the documentation, some of you will believe this, some will not.  What I hope is you”™ll avoid telling your students that weight management is just simple arithmetic.  Instead, please suggest that they shift their diets in a more healthful direction.

Joan Kent

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