But now science suggests it could be all down to your food intake. It seems it's how much you eat, rather than what you eat that counts. New research has suggested that consuming15 per cent fewer calories a day could help prevent age-related diseases and help you live longer.
Scientists at Pennington Biomedical Research Center found that simply eating less slows down the metabolism, a sign that the body is using energy more efficiently. It also causes less oxidative stress, a process that has been linked to cancer, diabetes and Alzheimer's.
For the study, 53 people between the ages of 21 and 50 were recruited and randomly assigned to either reduce their daily calories by 15 per cent or carrying on eating what they wanted for two years. Participants who restricted their calorie intake showed fewer signs of oxidative stress and slower metabolism, the team reports in the journal Cell Metabolism.
'Restricting calories can slow your basal metabolism, and if by-products of metabolism accelerate ageing processes, calorie restriction sustained over several years may help to decrease risk for chronic disease and prolong life,' lead researcher Dr Leanne Redman told the Daily Mail.
As the study was only two-years long, the researchers can't say how many years it could add to your life, but Redman suggests that cutting calories by 25 percent could extend life expectancy by seven years.
Always check with your GP before starting on a calorie-restricted diet.