A low-calorie diet will protect the cardiovascular system

Researchers from several American universities, including Duke University and Tufts University, conducted the first randomized clinical trial of CALERIE (from the English Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy – a detailed analysis of the long-term effects of reducing the amount of incoming energy), dedicated to studying the effect of a low-calorie diet on the adult body. The results showed that a low-calorie diet does not cause a number of metabolic effects observed in laboratory experiments on animals in people with normal or moderately overweight. However, its observance changes the severity of risk factors for the development of age-related diseases and the resistance of tissues to insulin.

A low–calorie diet is a diet that provides a reduction in the amount of calories entering the body and at the same time does not lead to a deficiency of important nutrients. Numerous animal studies have demonstrated the ability of a low-calorie diet to increase life expectancy and prevent the progression of a number of age-related diseases.

In laboratory animals, a low-calorie diet had a positive effect on life expectancy at the beginning of its observance at a young or early middle age. It would take several decades to conduct an equivalent study involving humans. However, shorter studies allow us to assess the possibility of following such a diet, as well as its safety and impact on quality of life, risk factors for the development of diseases, prognostic factors of life expectancy and the impact on target mechanisms identified during animal studies.

A total of 218 healthy men and women aged 21-51 participated in the CALERIE study. All participants were of normal weight or moderately overweight. While the participants of the control group throughout the study adhered to their usual diet and had a stable body weight, the participants of the experimental group were set a goal of reducing the caloric content of their diet by 25%. This was to ensure a 15.5% reduction in body weight during the first year and the stability of this indicator during the second year of the study.

In reality, the participants managed to reduce the caloric content of the diet by an average of only 12%, they adhered to this diet for two years. This ensured a 10% reduction in body weight during the first year and its maintenance at a new level during the second year. Despite the fact that the participants failed to achieve their goal, the results obtained demonstrate the most pronounced stable decrease in body weight in a clinical study of the effectiveness of a dietary approach involving people who are not obese. 

The study assessed the effect of a low-calorie diet on resting metabolic rate (adjusted for body weight) and body temperature. In many animal studies, a decrease in these indicators has been recorded against the background of a decrease in the caloric content of food, on the basis of which it has been suggested that these changes contribute to the phenomenon of increasing life expectancy. However, the data obtained demonstrated that a low-calorie diet had only a temporary effect on the metabolic rate at rest, and this change was no longer significant at the end of the study. No effect on body temperature was recorded at all.

Despite the absence of expected metabolic effects, the low-calorie diet provided a significant decrease in the values of a number of prognostic factors for diseases of the cardiovascular system compared to the control group. In particular, there was a decrease in blood pressure by 4% and the level of total cholesterol by 6% with a simultaneous increase in the fraction of high-density lipoproteins, or "good" cholesterol. In addition, the level of C-reactive protein in the blood of participants decreased by 47%. This protein is an inflammatory factor associated with cardiovascular diseases. Another important factor was a significant decrease in tissue resistance to insulin, which is an indicator of the risk of developing diabetes mellitus. The level of thyroid hormone triiodothyronine (T3) also decreased by 20%, while remaining within the normal range. This observation interested the authors, as there is evidence that reduced thyroid activity may be associated with a longer life expectancy.

In addition to clinical and laboratory indicators, the authors also assessed the effect of a low-calorie diet on mood (especially symptoms associated with hunger) and did not reveal any undesirable side effects. Of the reported side effects, they noted transient anemia developed in several participants and a decrease in bone density, the severity of which exceeded forecasts based on the degree of weight loss. These observations indicate the need for careful clinical monitoring during periods of compliance with a low-calorie diet.

Article by Ravussin E. et al. A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity is published in the Journal of Gerontology: Medical Sciences.

Evgeniya Ryabtseva

Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the National Institutes of Health:
NIH study finds calorie restriction lowers some risk factors for age-related diseases.