The effect of 14 popular diets did not last more than a year

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Scientists from Canada, China and the United States found that popular diets are about equally effective in reducing weight and improving the functioning of the cardiovascular system, but the effect of each of them disappears after a year. To do this, they conducted a meta-analysis of 121 works with almost 22 thousand participants: weight loss, changes in blood pressure and cholesterol concentrations for diets did not differ much in the first six months, but after a year all indicators returned to their previous values. Article published in The bmj.

The question of which of all existing diets is most effective is still open – largely due to the fact that when choosing it you need to take into account many different factors. For example, to reduce weight, it is best to monitor the amount of food consumed and the energy that a person spends: weight loss in this case provides a calorie deficit. On the other hand, for certain metabolic disorders, for example, a low-carb diet can help – even if weight loss is not observed. But with weight loss, such a diet is not more effective than that in which a low fat content is observed.

At the same time, the effectiveness of the diet should be evaluated not only as part of how weight is lost and health is improved during compliance, but also how long the result is maintained. It was this parameter that scientists decided to evaluate under the guidance of Long Ge from Lanzhou University. For their meta-analysis, they collected 121 studies, with a total of 21,942 participants who were overweight or obese.

Each study used one of 14 popular diets, divided into three groups: low-carb (for example, Atkins diet), low-fat diets (for example, Ornish diet) and balanced diets (for example, Mediterranean). In each study, there were control groups – participants who adhered to their usual diet. On average, the duration of the diet in each study was six months, but information on the health of participants was also available in all works a year after the change of diet.

In addition to weight changes, scientists also evaluated the effect of diet on blood pressure, the concentration of high and low density lipoproteins, as well as C-reactive plasma protein, the concentration of which increases with inflammation.

Compared to regular diets, both low-carb diets and low-fat diets over six months resulted in about the same weight loss (4.63 and 4.37 kilograms, respectively), and also reduced blood pressure equally effectively. For balanced diets, the effect was slightly less pronounced: average weight loss was three kilograms, and diastolic blood pressure decreased by 3.48 millimeters of mercury (compared to five and higher for diets low in carbohydrates or fats). In addition, low-fat diets have proven to be more effective in lowering low-density lipoproteins (the so-called “bad” cholesterol).

A year after the start of each of the diets, however, the weight returned to the indicator before the diet began – the same was true for the parameters of the health of the cardiovascular system. However, with the Mediterranean diet, the effect on the cardiovascular system persisted. The authors of the work noted that in order to achieve a better result, therefore, it is necessary to focus less on choosing a diet and pay more attention to how to maintain its result.

Losing weight and improving the functioning of the heart and blood vessels are far from the only goals pursued by people changing their diet. For example, a two-year-old study showed that a Mediterranean diet is good for preventing depression.

Elizabeth Ivtushok

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