Frequent small meals don't help weight loss: what research shows

Science does not support the rule of “eat often, but little”: the number of meals per day has almost no effect on calorie expenditure. According to research, this approach will not help most people lose weight.

The idea sounds logical: every snack sets off processes in the body that burn energy right away. That is partly true, but once you do the math, the picture changes.

Why frequent snacking achieves nothing

The body spends energy on digesting food. For a mixed diet that is roughly 10% of the calories eaten: out of a 700 kcal lunch, about 70 goes into processing the food.

It all depends on composition. According to a review by Dutch physiologist Klaas Westerterp, fats cost 0–3% of their energy, carbohydrates 5–10%, and proteins 20–30%. The effect grows with portion size, so in total there is no difference: paying in a shop with one hundred-crown note or five twenties comes to the same thing.

In a calorimetry chamber, where burned calories are calculated from oxygen use and exhaled carbon dioxide, volunteers were fed the same food for four days: three portions for two days, six portions for two days. Energy expenditure and fat burning did not differ, but with six portions people felt hungrier. In a two-month trial with obese people, those who ate three times a day and those who added three more snacks lost the same amount of weight.

The Prague experiment with two meals

A team led by Hana Kahleová at the Institute for Clinical and Experimental Medicine (IKEM) in Prague recruited 54 people with type 2 diabetes aged 30–70. For twelve weeks they followed a diet of six meals a day, and for another twelve weeks the same diet in two meals: a substantial breakfast between 6 and 10 a.m. and lunch between noon and 4 p.m. There was no dinner.

On six meals, patients lost an average of 2.3 kg; on two, 3.7 kg. Blood sugar and liver fat fell more, insulin sensitivity improved, and hunger, according to surveys, was felt less. But this is a result for people with diabetes and cannot serve as universal advice. For those taking glucose-lowering medication, regular meals are important, and habits should only be changed in consultation with a doctor.

Where the popular myth came from

Several older population studies showed that people who eat more often are usually slimmer. But in 1997, nutrition researcher France Bellisle and colleagues re-examined these studies and concluded that the link is very weak: the data come from questionnaires in which people wrote down what they ate themselves. Someone who is losing weight, or is embarrassed about their weight, tends to “forget” some snacks.

Where energy expenditure was measured accurately, no difference was found between frequent and infrequent eating. If the distribution of meals does affect weight, the authors believe it does so through the amount eaten, not through calorie burning.

Snack advocates also talk about “starvation mode”: supposedly, during long gaps the body stops burning energy. But the body has reserves: glycogen in the liver and muscles, and fat. Short fasting even raises expenditure: in a Vienna trial in 2000, eleven lean volunteers drank only water for 84 hours, and their resting energy expenditure rose by about 14% by the end because of norepinephrine. A real slowdown of metabolism begins only with an energy deficit lasting weeks and months of strict dieting.

Most energy goes into resting metabolism: breathing, the work of the heart and brain. You can influence it through muscle mass: a kilogram of muscle burns more at rest than a kilogram of fat. The second big item is movement, including climbing stairs and gardening. As for food, what matters is total energy intake and the share of protein. The number of meals is more a matter of convenience: frequent small meals are better with reflux, for older people with a poor appetite, and for athletes. Anyone who feels full on two or three meals has no need to force down snacks.

Around Prague, based on reporting by seznamzpravy.cz