Despite the popularity of 100-calorie portions in the first decade of this century, the concept of portion control is not always an attractive selling feature. This is because, too often, such portion designations fall short of a realistic helping. (Everyone knows that, no matter its size, a bag of chips is a single serving!)
The most natural way to integrate portion control into any weight-management approach is to select foods that contribute to satiety, that is, how satisfied and not hungry one feels between meals. Foods with a high satiety value stave off hunger, reducing “next-meal” consumption.
Two hormones influence the hypothalamus into effecting satiety and energy expenditure. Leptin, secreted by adipose (fat) tissue, increases satiety. Ghrelin, secreted by specialized cells in the gastrointestinal tract, signals hunger.
Due to the increasing popularity of high-protein diets, many people feel high-protein foods are superior at producing satiety. Yet results of a 2013 study in the American Journal of Clinical Nutrition comparing the satiety value of a high-protein egg and beef breakfast against a same-calorie, normal protein breakfast and breakfast skipping, proved interesting.
The study’s subjects were obese teenage girls. Lunch was the same, “normal-protein” meal for all groups. Dinner and snacks were not controlled. The high-protein breakfast resulted in less snacking on high-fat foods at the end of the day, and more immediately favorable hormonal and neuronal signals associated with regulation of food intake. Daily energy intake was lower in the high-protein group compared to the normal protein group.
The surprise came, however, when satiety remained the same for the group that skipped breakfast. Moreover, a study published just last month in the Journal of the American College of Nutrition, compared the satiety of an egg-based breakfast to the same-calorie bagel-based breakfast in children and adolescents. When it came to “next-meal” food consumption, there was no difference in any group.
A popular narrative is that a macronutrient distribution favoring protein and fat over carbohydrate, negates the simple physics of weight control: Calorie consumption that exceeds energy needs equals stored body fat, regardless of the calories. It’s also become popular to boast that nutritionists were wrong, and all calories are not created equal. This perpetuates the “only carbs” make us fat paradigm, or at the very least, that carbohydrates are primarily responsible for the epidemic of obesity.
Such false reasoning is rooted in the observation that most dietary carbohydrates raise blood insulin levels. Since insulin is required for fat cells to take glucose out of the blood and convert it to body fat, it has been christened the “fat-storage hormone.” Coupled with this assertion is the suggestion that carbohydrates contribute little to satiety. This narrative is inconsistent with the “satiety index” and the fact that most of the insulin-stimulated blood glucose uptake is by muscle cells. However, muscle cells convert glucose into glycogen, a critical energy store.
The satiety index gauges fullness subsequent to eating a measured amount of food. The standard used for comparison is white bread, which is given a score of 100. Any food that conveys a feeling of fullness and reduced next-meal calorie consumption more effectively than white bread receives a higher score.
By this measure, the food with the highest satiety value by far is the lowly boiled potato. Standing at number three is porridge made from oats. This is consistent with a study in the 2015 “Annals of Nutrition and Metabolism,” which found oatmeal superior to dry cereal with respect to reducing next-meal consumption. Oats are rich in soluble fiber, known to convey satiety.
The fact is, most complex carbohydrates and sources of protein score quite well it comes to satiety, as do many fats. Fat slows digestion, so a meal with some healthy fat helps to stave off hunger. Fat also provides “mouthfeel,” a pleasing texture that can enhance satiety. (This could help explain why several studies demonstrate that moderate intake of nuts aids in weight control.)
For this reason, it is important to recognize that all healthy foods can contribute to satiety. Balanced diets of whole foods are mixtures of protein, fat, and complex carbohydrates. To focus on a single macronutrient in a single portion, in the end, is nothing more than a marketing strategy, rather than a nutritional one.
There is considerable science behind 'feeling full.'