When they talk about speeding up the metabolism, it is usually suggested to do it either with the help of certain foods, or by changing eating habits – for example, switching to fractional meals. The idea of the latter is that a large number of meals “accelerates” the metabolism, since more energy is spent on its digestion and absorption – the same thermal effect. But in fact, there is no difference how much energy is spent on the thermal effect with different numbers of meals, if the total intake is the same. It is possible to increase the thermal effect by consuming more calories, but is it necessary?
Some foods – like chili peppers and coffee – can slightly increase metabolism (and the mechanisms of their effect on fat oxidation and thermogenesis are clear), but their effect is so slight and short-lived that it will not affect body weight or volume in any way. Advertisements for “metabolic rate-enhancing” foods and supplements are based on questionable, poorly conducted, and paid-for by dietary supplement manufacturers. Numerous supplements that are positioned as “burning fat” in reality simply cannot work: it is impossible to introduce into the body a substance that is capable of breaking down fat molecules in adipose tissue and removing them. In addition, such supplements have undesirable effects on the liver – and some unlucky people losing weight in the United States took them to the transplant department . Ephedrine supplements are generally banned by the US FDA: according to a 2003 meta-analysis, they have psychoactive effects and adversely affect various systems, including the cardiovascular system.
Dietary supplements have not been tested for safety in the same way as medicines. They are not able to speed up anything (except for spending money), but they can additionally contain strong laxatives and diuretics, as well as prescription drugs for the treatment of obesity, which are prescribed according to strict indications and are taken under the supervision of a doctor. These components may not be listed at all on the labels.
The only way to gradually increase basal metabolism is to increase the volume of metabolically active tissues. More energy is spent on servicing the muscles, so its consumption will increase slightly. But there are no magic, quick and at the same time safe means to increase metabolism. As with everything that relates to the human body, the main principle should be “do no harm” – that is, do not starve, do not try on yourself severe food restrictions and “fast” diets. Extreme diets force the body to turn on the economy mode in order to make better use of the incoming food. Basal metabolism slows down , the synthesis of signaling molecules that control feelings of hunger and satiety changes .
With weight loss, a slight decrease in basal metabolic rate is logical, because you need to maintain the vital activity of a smaller number of tissues (although adipose tissue accounts for a little, 3-4% of the basal metabolic energy) – but with extreme diets this decrease exceeds expected. This leads to an interesting phenomenon : the body resists weight loss with all its might, but easily regains it. This is why there are no simple, easy and quick fixes in evidence-based nutrition.