Two-Year Calorie Restriction Trial in People Shows No Clear Difference in Telomere Length

In a randomised trial applying long-term calorie restriction in people, changes in the length of telomeres, the protective structures at the ends of chromosomes, did not give a consistent conclusion. Researchers at Pennsylvania State University, Columbia University and elsewhere in the United States analysed data from the CALERIE 2 trial and reported the results in Ageing Cell.

Non-Obese Adults Aged 21 to 50, Randomised for 2 Years

CALERIE 2 was a trial in which healthy men and premenopausal women with a body mass index of 22.0 to 27.9 were randomly assigned 2 to 1 to a 25% calorie restriction group or an ad libitum (free-eating) group and followed for 2 years. The researchers measured telomere length in the blood of 175 people at baseline, 12 months and 24 months using two methods: quantitative PCR and a DNA methylation-based estimate (DNAmTL).

In the intention-to-treat analysis, there was no significant difference in telomere decline over the first year, and in fact the restriction group tended to show more decline. When the actual degree of restriction was taken into account, greater restriction was associated with a larger decline in DNAmTL in the first year, a period of weight loss, but in the second year, a period of weight maintenance, the restriction group had a smaller decline in PCR telomere length. Over the full 2 years, there was no difference.

The actual average calorie restriction was about 12%, short of the target. The researchers said it is still unclear whether this result reflects lasting damage, an adaptive response to energy shortage, or measurement error or insufficient statistical power.