Obesity Energetics: Body Weight Regulation and the Effects of Diet Composition

Abstract

Weight changes are accompanied by imbalances between calorie intake and expenditure. This fact is often misinterpreted to suggest that obesity is caused by gluttony and sloth and can be treated by simply advising people to eat less and move more. However, various components of energy balance are dynamically interrelated and weight loss is resisted by counterbalancing physiological processes. While low-carbohydrate diets have been suggested to partially subvert these processes by increasing energy expenditure and promoting fat loss, our meta-analysis of 32 controlled feeding studies with isocaloric substitution of carbohydrate for fat found that both energy expenditure (26 kcal/d; P <.0001) and fat loss (16 g/d; P <.0001) were greater with lower fat diets. We review the components of energy balance and the mechanisms acting to resist weight loss in the context of static, settling point, and set-point models of body weight regulation, with the set-point model being most commensurate with current data.

Low Carbohydrate and Low Fat Diets with Equal Protein Content Lead to Similar Improvements in Body Composition and Glucose Tolerance in Obese Mice subjected to Caloric Restriction

“…However, this difference between the diets was not significant and can hardly be used as evidence in support of recent findings in human studies that low carbohydrate diets lead to greater energy expenditure compared to low fat diets (16). Our results are in agreement with many human studies that reported no practically meaningful differences in energy expenditure between the isocaloric and isonitrogenous low fat and low carbohydrate diets (33,35,45).…”

“…However, a large number of studies contradicts the carbohydrate-insulin model of obesity. Meta-analysis of 32 controlled feeding studies with substitution of carbohydrate for fat show that fat loss and energy expenditure were greater for low fat diets compared to low carbohydrate diets though differences between the diets in fat loss (16 g × d -1 ) and energy expenditure (26 kcal × d -1 ) were rather small (35). A recent randomized clinical trial which engaged over 600 participants showed no difference between low fat and low carbohydrate diets in weight loss during a 12-month period, and neither baseline insulin secretion nor genotype pattern was associated with the dietary effects on weight change (33).…”

Persistent effects of obesity: a neuroplasticity hypothesis

“…Although reducing caloric intake often results in immediate weight loss, it is difficult to maintain over the long term. 4 This also occurs in animals. For example, it has been known since the 1980s that obese rodents maintain a higher average body weight than those that were never obese, even when maintained on identical diets.…”

The evolution of body fatness: trading off disease and predation risk

“…Furthermore, under the settling point model, we would not expect to see any compensatory changes in energy expenditure or intake to resist changes in energy balance -yet such changes are routinely observed (Norgan and Durnin, 1980;Leibel et al, 1995;Horton et al, 1995;Dulloo et al, 1997;Dulloo and Jacquet, 1998;Goldberg et al, 1998;Weyer et al, 2001;Galgani and Santos, 2016;Hall et al, 2011Hall et al, , 2012Johannsen et al, 2012;Polidori et al, 2016). A review of 32 controlled feeding studies in humans concluded that the responses were most consistent with the set-point rather than the settling point model (Hall and Guo, 2017).…”