Or perhaps they just didn't have as much to eat. Yoga masters, for instance, heirs of an ancient healing tradition, will tell you to stop eating before you feel full.
It's long been thought that restricting food intake can extend lifespan. In a 1930s US study, rats on a calorie-restricted diet were found to live twice as long as normal. Those findings have since been tested on other animals and found to hold generally true. However, there has been no scientific evidence until now to show that the same holds true in humans.
A new study by researchers at Saint Louis University in the USA tackled this issue. Edward Weiss and his team tracked levels of the thyroid hormone triiodothyronine, or T3, in three groups of healthy middle-aged individuals. The first group of volunteers was placed on a calorie-restricted diet for a year. This involved eating 300-500 calories less per day (equivalent to a rich dessert or a burger and fries). The second ate a normal diet, but exercised regularly. The third made no change in their lifestyle.
The results were clear: although people in the first two groups lost body fat mass, and the exercisers became fitter, T3 levels rose most in the calorie-restricted group.
This is important because T3 helps regulate metabolic rate and "tissue ageing". The bodies of the restricted eaters reacted to smaller food intake by making more T3 and lowering the metabolic rate to cut energy expenditure.
The mechanisms of ageing are still not understood, but the thinking goes that consuming less means the body can more efficiently break down and absorb nutrients, minimising the storage of excess as fat. This helps stabilise blood sugar levels, reduces strain on the organs, and also means less free radicals, hence lower oxidative damage (suspected of causing cancers).
But just eating less is not enough: one has to eat nutritious food and live a healthy lifestyle. Simply eating too little can cause malnutrition, which actually speeds up aging. Be careful if you choose to experiment with your lifespan
