Research published in Cell Metabolism last week suggested that people reducing calorie intake by 15 percent lowered their risk of age-related disease.

Participants in the calorie reduction group saw a drop in metabolic rates following one year; and a fall in oxidative stress in the second. Oxidative stress has been linked to several age-related conditions, such as diabetes, heart disease, cancer and Parkinson’s disease.

The study was led by Leanne Redman, an associate professor specialising in Biomedical Research at Louisiana State University.

What did the study involve?

As part of a series titled the Comprehensive Assessment of the Long-term Effects of Reducing Intake of Energy (or CALERIE), researchers had previously undertaken pilot studies to determine what kind of calorie reduction programme would be feasible to maintain, and which type could have an impact on the biomarkers of aging.

Participants were aged between 25 and 50, with BMIs ranging between 22 and 28 at the start of the study.

They were provided meals for the first 27 days to help coach them on achieving the right weight loss trajectory (through portion size and energy content guidance).

After this, they continued to receive guidance from clinicians and nutritionists, but were permitted to eat what they pleased. They were given supplements to ensure they maintain healthy levels of vitamins and minerals. They were also issued with graphs and a scale to track their progress. Weight measurements were used to determine the level of calorie intake and reduction over the study period.

The programme actually targeted 25 percent calorie reduction; however 15 percent was the level of calorie reduction which was achieved.

What were the results?

The average amount of weight lost over the two years was 8.7kg (compared to an increase in the control group of 1.8kg).

Participants in the study group also saw a drop in metabolic rates, indicating their bodies were using calories more efficiently. The rate of energy expenditure over 24 hours in study subjects was 80-120 kcal lower than anticipated when taking weight lost into account.

Researchers used a type of prostaglandin called F2-isoprostane as a biomarker for oxidative stress. Following year 1 and year 2 in the study group, levels of F2 were ‘significantly reduced’; but remained the same in the control group.

It is thought that oxidative damage causes the body to age faster, and it has been linked by some to conditions such as Parkinson’s, Alzheimer's and cancer.

What do the results mean?

The final analysis was based on 53 people (a study group of 34 and a control group of 19) which by clinical trial standards is a relatively small pool. However, given the scale and duration of the study, implementing it even at this size would have been a huge undertaking.

That said, the results do seem to be promising.

The study has been hailed as a breakthrough by a biologist from the University of Aberdeen, as it is the first to be carried out on humans on such a scale, and seems to correlate with theories previously developed following similar studies on rodents; that calorie restriction could be linked to longer life, due to its effects on metabolism and oxidative stress.

While it is difficult at this stage to infer from these results that calorie restriction leads to longer life, it does support the notion that it leads to healthier and better quality of life.

The authors maintain that more studies need to be carried out to explore what is, at present, still an area of research at a relatively early stage.

Study leader Leanne Redman proposed that it would be useful to reconvene study subjects at a later date to see what the long-term impacts of the programme are.

You can read the full study here.