Eat Less, Live Longer: Can Humans Do it?

Caloric restriction among mammals whose body mass index is normal, defined as eating about 25% fewer calories than one would during ad libitum intake, increases life span in many species.

Caloric restriction (CR) among mammals whose body mass index is normal, defined as eating about 25% fewer calories than one would during ad libitum (AL) intake, increases life span in many species. Most researchers believe that humans are capable of reducing intake sustainably. The Journal of Gerontology has published results from a recent trial that indicate that the prevailing view may be wrong. Some people can practice CR with good results on their overall health.

This multinational team of researchers enrolled 218 human participants between the ages of 21 and 51 years to a randomized intervention study. Participants either remained on AL intake, or reduced caloric intake 25%. The researchers looked at CR’s feasibility, safety, and effects on predictors of longevity.

Participants' average BMI was 25.1, with a range of 21.9—28.0kg/m2. Eighty-two percent of CR and 95% of AL participants completed the study.

Participants who practiced CR were overall not able to maintain a 25% CR (which would have been a daily calorie reduction of about 500 calories) for the duration of the study. They did, however, reduce their caloric intake by about 234 calories/day on average. They also experienced a significant weight load of about 7 kg.

Participants in the AL arm lost an insignificant amount of weight.

Change from baseline resting metabolic rate adjusted for weight change, called RMR residual, decreased more in CR than AL at one year, but no further changes were noted at 2 years. In the CR group, plasma triiodothyronine was lower than in the AL group at 1 and 2 years. Tumor necrosis factor-α was significantly lower only at the end of 2 years.

Participants in the CR arm had larger decreases in cardiometabolic risk factors without adverse effects on quality of life.

The authors conclude that despite the fact participants did not reduce their calorie intake to the target 25%, smaller magnitudes of CR are feasible in non-obese humans and can lead to potential benefits for aging-related outcomes.