Why do diets work?

Around the 70s of the last century, dietary advice for Americans first appeared in restrictions. People were first recommended to limit themselves in sweets and fat. Throughout history up to this point, the biggest problem was that people were undernourished. With the increasing wealth and availability of cheap and caloric sources of food, the pendulum swayed in the other direction and people began to overeat. So swayed that today in the world more people are dying from diseases related to overweight than from hunger, this was recently reported in the prestigious medical publication The Lancet! Around the same years of last century, dietology began to be associated with weight loss. Today, the word diet almost always means this or that way to lose weight, although in itself this concept means just a style of diet in the most general sense of the word. For over forty years, the efforts of millions of people have been focused on finding the answer to the question “what to eat to lose weight”.

Diets with high protein content

Why do diets work?

A high-protein diet is considered a diet where the proportion of protein is 30-60% of the total calories. If measured in grams, it is 1.2-1.6 g/kg of body weight. At the same time, twice the official norm of a sitting person (1.6 g/kg vs. 0.8 g/kg) was more effective for muscle retention and fat reduction. Recently, it was found out that when combining diet and high-intensity training (interval sprints and power training), even higher protein content (2.4 g/kg) was even more effective for muscle growth and fat burning. Several recent meta-analyses support the benefit of high protein content in food for slimming and keeping muscles on diets. Another systematic review found that 2.3-3.1 grams of protein per kilogram of dry weight can be recommended for slim people on diets who are engaged in strength training. Protein plays a major role in dieting for weight loss. Of all macroelements, it is energetically most expensive: the body spends 20-30% of the intake of calories on its digestion and absorption (for carbohydrates it is 5-10%, for fats – only 0-3%). In addition, protein is the most nourishing of all macroelements and helps control appetite and hunger better. So low-carbohydrate and low-fat diets are effective in that they usually contain more protein.

Keto Diets

Why do diets work?

Keto diet – a diet in which carbohydrates are reduced to 50 grams per day and less. In the absence of glucose, the body switches to an alternative fuel – ketone bodies, which are produced from dietary fats and body fat, if a person is in calorie deficiency. It is believed that by eliminating carbohydrates, oxidation of fats and fat burning can be accelerated, because insulin does not interfere with the process. That is, the benefits of carbohydrate elimination here go beyond a simple calorie reduction. It is also believed that the production and use of ketone bodies creates a unique metabolic state in the body, which should create better conditions for fat loss. In support of this idea, a recent meta-analysis has found that a ketogenic diet suppresses appetite better than a regular low-calorie diet. But despite a large number of studies on carbohydrates and their effect on weight loss, single individuals controlled the total amount of protein and calories for the purity of the experiment. And those who did, did not show any advantage of a weight loss keto-diet over a normal calorie restriction.

Periodical fasting

Periodical fasting is a temporary refusal to eat, which helps to reduce the average calorie per week. The most common options:

  • The alternation of days. This is the most studied option. It is allowed to eat in the interval of 12 hours and starve for 36 hours. Or eat for 24 hours and starve for the next 24 hours. Or to eat for 24 hours and starve for the next 24 hours is very little (not more than 500 kcal). There is no full compensation for calories during the “full” days, so the person is still in a calorie deficit and losing weight.
  • Hunger is a few days a week. Two days a week a person does not eat or severely limits calories. Although it is effective for weight loss (by creating a total calorie deficit per week), scientists found no difference in weight loss between a group of hungry people a few days a week and a group of people who had a moderate calorie deficit every day for six months.
  • Restricted meals by time during the day. The fasting period of 16-20 hours is followed by a meal period of 4-8 hours per day. The most studied form is Ramadan, during which believers starve from sunrise to sunset for about a month.

In general, periodic fasting and regular meals with a uniform calorie deficit are similar in effect. Both lead to weight loss, but in case of prolonged fasting, muscles are more likely to lose along with fat.