Longevity Briefs: Does Calorie Restriction Prevent Telomere Shortening?

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Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

Telomeres are protective caps on the ends of our chromosomes. Each time a cell divides, its telomeres become shorter, eventually leaving it unable to divide any further. This process is called telomere attrition, and is thought to be one of the main reasons we age.

Calorie restriction involves cutting calorie intake significantly below daily requirements, but without causing malnutrition. We know that calorie restriction puts our cells into a kind of ‘survival mode’ in which growth is slowed and self-repair systems are activated. For this reason, scientists expect that calorie restriction should slow down telomere attrition. This appears to be the case in mice, but more evidence is needed to confirm it works in humans. In this study, researchers looked at how telomere length changed during a long-term study of calorie restriction. They got some perplexing results.

The discovery:

Researchers analysed data from the CALERIE study, a clinical trial in which healthy 21-50 year-olds were randomly assigned a 25% reduced calorie diet or to eat whatever they wanted for two years. Specifically, they looked at telomere length based on blood samples from 175 CALERIE participants. Contrary to what the researcher had hypothesised, the rate of telomere loss in the calorie restriction group actually sped up during the first year of the study, with participants in this group suffering more telomere attrition than those in the control group. In the second year, however, telomere loss in the calorie restricted group slowed down. When taking the entire two year study period into account, there was no significant difference in telomere loss between the two groups.

Graphs showing average telomere length at the start of the study and after 12 and 24 months in participants eating normally (blue) and on calorie restriction (red). The two graphs correspond to different methods of measuring telomere length.
Effect of long-term caloric restriction on telomere length in healthy adults: CALERIE™ 2 trial analysis

The implications:

So, it appears as though calorie restriction may actually accelerate telomere attrition during the first year, at least in healthy people below the age of 50. This is a surprising finding and will have to be corroborated by other studies. The authors suggest that it may take some time for the body to make metabolic adaptations to a long-term calorie restricted diet, during which time telomere maintenance is deprioritised. It’s also hard to make generalisations based on a single study because there are many variables, such as the extent of calorie restriction, the methods used to restrict calories (such as intermittent vs continuous fasting), the age and health status of the participants and so on.

Participants of the CALERIE trial will be followed up when 10 years have passed since the start of the study, which may tell us whether there were any longer-term effects on telomere length. In the meantime, though, this study shouldn’t put anyone off calorie restricted diets. While the effects on telomere length are still unclear, the CALERIE trial showed very significant health benefits in the calorie restriction group. These included weight loss, reduced cardiovascular risk factors (such as reduced blood pressure and improved cholesterol balance) and improved sensitivity to the blood sugar lowering hormone insulin.