The effect of fat on appetite

The type of food we ingest (high fat vs high carbohydrate, junk vs nutritious) has the ability to force us into eating more than we should have by actually increasing hunger signals and postponing satiety.

When ingested with salt, sugar, and refined carbs, (e.g., the typical fast food meal), self-regulation becomes very difficult. The quality of the food we eat determines the efficacy of the hunger-satiety switch. Part of the trick is consciously switching over to foods with higher nutritional density (as a function of calories). This way we give the body the ability to re/learn experience true physiological hunger, rather than be at the mercy of the toxic effects of unhealthy food.

Here’s an excerpt from “Control of Food Intake in the Obese,” by J.E. Blundell and A. Gillett, Obesity Research, Vol 9, 2001. It shows how food choice in and of itself (exclusive of its caloric level) can lead to weight gain.

“Adjustments to the signaling of hunger and satiety will affect the pattern of food consumption in weight-gaining or obese individuals; this will be manifested through an increase in the size or frequency of eating episodes. However, energy intake could also be raised through the consumption of high energy-yielding foods. There is considerable evidence that high-fat diets lead to positive energy (and fat) balances, which, in the absence of a capacity for fat oxidation, will lead to weight gain. There is a much greater prevalence of obesity among habitual high-fat than low-fat consumers when the quality of the data are improved by omitting implausible self-reports of food intake. In addition, obese women show a strong preference for sweet high-fat foods, which is matched by high consumption of foods with a combination of high-sugar and high-fat content. Moreover, in contrast to normal-weight subjects, obese individuals select more high energy dense and fewer low energy dense foods. The proposition that a positive energy balance is brought about by the energy density of foods rather than by the fat content is not supported unequivocally by evidence. There is considerable evidence that people do not maintain a uniform weight of food intake when the energy density changes. Moreover, the highest energy densities can only be achieved by the inclusion of large amounts of fat (the macronutrient with the highest energy density). There is also evidence that fat itself may weaken the regulation of food intake. Subjects given a high-fat diet for 3 weeks strated higher hunger levels at the end than at the beginning of the period. This finding resonates with the finding that although higher carbohydrate meals raise leptin levels, high-fat meals actually reduce 24-hour plasma leptin concentrations. Consequently, a high-fat intake contributes to a positive energy balance directly by increasing the amount of energy consumed (perhaps through passive overconsumption) and also by increasing the drive to eat through increased hunger levels. It follows that individuals who possess the trait of high hunger levels and the trait of high-fat food preference would possess a considerable risk of achieving a positive energy balance. It is possible that these traits are linked through the mediation of leptin.”