What makes you full?
To keep the metabolism going, the organism depends on regular food intake. The feeling of hunger signals to the body when food is needed, the feeling of fullness keeps us from eating — but do we still pay enough attention to this nowadays? The range of “fast foods” on offer — be it snacks from the bakery, a drink from the vending machine or the bar in between meals — are consumed quickly and, above all, in excess without leading to an adequate satiety response. “Fast foods” cause hunger to be all the greater at the next meal and lead to an even higher energy intake. But what keeps us fuller in the long term?
What is satiety actually?
Satiety and the feeling of fullness are central concepts in the understanding of appetite control. Satiety occurs during eating, and the feeling of fullness sets in after eating and prevents further food intake before hunger returns. Improving satiety and the feeling of fullness is considered a central means of weight control. Many studies have examined the various factors that can potentially contribute to the inhibition of eating.
No “fast eating.”
Controlled dietary intervention studies have shown that drinking simple energy-dense beverages that are consumed very quickly does not result in lower intake of other foods — that is, it does not contribute to satiety. One of the theories behind this observation is that rapidly ingested calories are not well perceived by the sense of taste and do not lead to an adequate satiety response. This idea is supported by the results of a number of studies that have shown that the low satiety response of beverages can be largely attributed to their short retention time in the mouth. Keeping food and drinks in the mouth longer has been shown to result in earlier meal termination and a higher satiety response. How can this be? Several recent studies showed that eating slower leads to higher levels of satiety hormones. These findings are consistent with the idea that the sense of taste is a nutrient sensor that informs the brain and gut about the influx of nutrients. Thus, the sense of taste contributes to the satiating effect of food.
Listening to the stomach
A number of studies showed that stomach distention is an important stimulus for finishing a meal. During eating, the extent of stomach distension is registered by means of so-called mechanosensors and transmitted to the brain — more precisely to the hunger and satiety center in the hypothalamus. The higher the volume of a meal, the more the stomach wall stretches. The extent of the stretching varies greatly from individual to individual, but can be influenced in the long term by the amounts of food consumed. The fact is: with very high-energy but compact meals, we do not experience the same feeling of satiety as with voluminous but lower-energy meals. The absorption of further food usually stops when the distention of the stomach exceeds about 20% of the normal size. Foods rich in fiber and water, such as vegetables and legumes, soft fruits and citrus fruits, and mushrooms, provide sufficient volume.
Better hard than soft
Modern food offerings are often dominated by a wide variety of energy-dense, soft-textured foods because they can be consumed more quickly. However, many studies suggest that large bites and lack of chewing activity contribute to lower satiety from these foods. A study from the Netherlands demonstrated that hard foods resulted in reduced energy intake compared to soft foods of equivalent energy. In terms of quantity, 32% less of hard foods were eaten overall than soft foods. Despite the lower energy intake, all subjects in the study felt equally full, indicating that differences in food hardness lead to a sustained reduction in energy intake throughout the day. So changes in food texture could be a helpful way to reduce total daily energy intake.
Mix consistencies
Researchers have been able to show that satiety is linked to the speed of gastric emptying. The longer the food pulp remains in the stomach and intestines, the longer satiety lasts. Liquid foods pass through the gastrointestinal tract rather quickly. This explains, at least to some extent, why soft drinks in particular hardly lead to satiety, despite their sometimes high energy and sugar content. Food that first has to be broken down, on the other hand, lingers longer in the digestive tract. Digestion of the individual nutrients takes different amounts of time. Carbohydrate-rich foods pass through the stomach most quickly. Protein components linger a little longer, while fats delay gastric emptying the longest. A liquid smoothie bowl with solid protein and fat toppings (peanut butter, granola, vegan protein powder, etc.) would be one of the countless examples of optimal “consistency food.”
Same calorie content, different satiety levels.
Different foods have different levels of satiety — despite the same calorie content. In a study by Holt et al, the satiety properties of a variety of foods were compared to the satiety power of white bread (100%). Potatoes (323%), fish (225%), oatmeal porridge (209%), and whole grain pasta, apples, and oranges stood out at nearly 200%.
So what makes you feel full the fastest?
For optimal satiety, a smart mix of nutrients is beneficial. Complex carbohydrates in the form of vegetables, legumes, soft fruits, mushrooms and nuts, which cause a slow rise and fall in blood sugar, are preferable in combination with high-quality proteins and fats. Dietary fibers, indigestible carbohydrates, have a mechanical satiety effect due to their volume — they stretch the stomach, but also the entire small intestine. In addition, intestinal bacteria form volatile fatty acids, which lead to the production of satiating hormones in the large intestine.
Meat, fish, dairy products and legumes are considered to have a particularly high satiety potential. Studies have shown that energy from proteins is more satiating than energy from carbohydrates or fat.
Why this is the case has not yet been conclusively researched. It is suspected that the amount of circulating amino acids in the blood influences the satiety center in the brain and stimulates the formation of satiety hormones. In overweight study participants, administration of a mixture of phenylalanine (3 g), valine (2 g), methionine (2 g), and tryptophan (1 g) caused a 22% decrease in food intake.
Coffee against hunger — how does it work?
Caffeine is a so-called stimulant with a stimulating effect on the psyche, increases drive and concentration and eliminates symptoms of fatigue. A distinction is made between a stimulating and an excitatory effect of caffeine, the latter requiring a higher dose. At low doses, the stimulant effect of caffeine is almost exclusively evident, i.e., basic psychological functions such as drive and mood are affected. Higher doses also stimulate the respiratory center and the circulatory system. Through complex mechanisms, caffeine thus leads to an increased release of sugar from the sugar stores of the liver and to the metabolism of fats stored in fat cells. Caffeine thus mobilizes our energy stores, so that we experience a feeling of satiety — even if only for a short time — as more sugar and fatty acids from our own energy stores circulate in our blood.
Good news: sweeteners satiate without consequences
The consumption of sugar-sweetened beverages is one of the main problems of global obesity. Therefore, replacing sugar with low-calorie sweeteners is an effective strategy to control weight without giving up sweetness. It is often assumed that “fake sweetness” fools the body into craving real, energy-rich sugar all the more. In a study, however, it was shown that when food alternatives sweetened with stevia were consumed, the “lack of energy” was not compensated, however, by eating more in subsequent meals. On the contrary — the participants reported a similar feeling of satiety as when eating the high-sugar original.
Text Sources:
(1) Taschenatlas Ernährung (Biesalski HK, Grimm P, Nowitzki-Grimm S; Thieme Verlag 2015)
(2) Ernährungsumschau: Hunger und Sättigung (Langhans, W; Ernährungsumschau 2010)
(3) de Graaf C. Texture and satiation: the role of oro-sensory exposure time. Physiol Behav. 2012 Nov 5;107(4):496–501. doi: 10.1016/j.physbeh.2012.05.008. Epub 2012 May 15. PMID: 22609070.
(4) Forde CG, van Kuijk N, Thaler T, de Graaf C, Martin N. Oral processing characteristics of solid savoury meal components, and relationship with food composition, sensory attributes and expected satiation. Appetite. 2013 Jan;60(1):208–219. doi: 10.1016/j.appet.2012.09.015. Epub 2012 Sep 24. PMID: 23017464.
(5) Bolhuis DP, Forde CG, Cheng Y, Xu H, Martin N, de Graaf C. Slow food: sustained impact of harder foods on the reduction in energy intake over the course of the day. PLoS One. 2014 Apr 2;9(4):e93370. doi: 10.1371/journal.pone.0093370. PMID: 24695412; PMCID: PMC3973680.
(6) Holt SH, Miller JC, Petocz P, Farmakalidis E. A satiety index of common foods.
Eur J Clin Nutr. 1995 Sep;49(9):675–90. PubMed PMID: 7498104.
(7) Peter C. Heinrich, Georg Löffler: Biochemie und Pathobiochemie. 9., vollständig überarbeitete Auflage. Springer, Heidelberg 2014, ISBN 978–3–642–17971–6, S. 470–471.
Image Sources:
