Can eating less extend your life?
Reducing calorific consumption has been a key consideration in health nutrition for as long as the study has existed and for as long as we have had an abundance of food to eat. When people decide to reduce the number of calories they consume the reason is almost always to lose weight. The motivation for this can be to improve outward physical appearance, improving day to day health and even to avoid an early death due to conditions such as obesity and type-2 diabetes. However there may be an additional and much greater benefit in reducing the amount of calories that we consume as it may enable us to live and remain healthier for longer.
Animals that eat less live longer
Numerous studies into animals and other lifeforms such as yeast, worms, spiders, fish, mice and monkeys have shown that restricting calories extends life span.
In 1984 Professor Roy Lee Walford, M. D., author of the ‘120 Year Diet’, conducted a series of calorie restriction experiments with mice in which he was able to extend the life of a mouse from an average age of 36 months in the control group to over 48 months in the calorie restricted group. In human terms this would be the equivalent of increasing ones life span from an expectancy of 100 years to an extended life expectancy of 180 years.
In an million dollar study by the University of Wisconsin, 76 rhesus monkeys were split into 2 groups, the control group fed on a normal diet whilst the test group is fed on a diet of 30% less calories. At an older age those in the calorie restricted test group displayed a more youthful and healthy appearance whilst monkeys from the control group appeared much less healthy and less energetic. A previous study from 1987 by the National Institute on Ageing also on rhesus monkeys found evidence of health benefits but no evidence of increased median lifespan.
Calorie restriction in humans
There is currently no conclusive evidence that calorie restriction has the same effect on humans as it does with animals. Human’s longer lifespans relative to the age of this area of study does mean that the scientific data available so far is limited. This is made even more difficult by how hard it is to maintain a prolonged calorie restricted diet which can involve obsessive planning, measuring and portion control, eating salads on an industrial scale and even lengths such as eating only the peel from fruit whilst disgarding the flesh.
One of its longest practitioners is British man Dave Fisher who has been restricting his diet to just 1,600 calories per day (an average of 2,000 is the recommendation) for over 20 years. At the age of 51 this gave him what doctors agreed was the body and skin of a 32 year old. However on a cellular level the benefits were not so clear cut. The length of Fisher’s telomeres were measured and when compared to a man of the same age the length did not indicate lesser effects of ageing.
One of the main factors involved in calorie restriction is slowing down metabolism. Metabolism comes from Greek, meaning ‘rate of change’. It is broken down into two categories of catabolism – breaking food down into fuel, and anabolism – using energy to build new cells. By reducing calorific consumption over a long period, scientists believe that a genetic survival switch is flipped and that a body’s metabolic rate slows down to deal with possible starvation of replacement fuel. One side effect of this is that it becomes more difficult to keep warm, made worse with less body fat for insulation. However there are benefits. A study by the University of California found a slower rate in loss of brain cells in those on a restricted calorie diet as well as being less susceptible to disease overall.
Evolution on an empty stomach
Many scientists believe that as humans have spent the vast majority of our evolution as hunters and foragers, that our bodies are naturally designed to adapt to consuming lower calorie diets. Modern notions such as breakfast, lunch and dinner would have been and essentially still are alien to a species that has historically only eaten to survive. It is only with the dawn of modern farming and production that food has become abundant enabling us to rely on the consumption of high calories on a regular basis.
Whilst obsessive calorie restriction diets may seem like an extreme measure in a society comfortable with over eating, one thing it does reinforce universally is that packing a higher amount of nutrients into a smaller number of calories is a healthier path. Trends which pay testament to this include the rise in popularity of natural super-foods, as well as the rise in functional health foods such as vitamin drink shots that try to formulate a similar type of product. In contrast is falling sales for diet food brands such as Weight Watchers, which despite being low in calories are also very low in nutrients. Even junk food is having to change its ways as sugar is increasingly demonised by the media and replaced with low or zero calorie natural sweeteners such as stevia.
In addition to reducing calorific input, a further step towards calorific optimisation would be better digestion. By maintaining good gut health and by eating the right combinations of foods, thereby making it easier for digestive enzymes to break them down, it is possible to be much more successful in maximising the absorption of nutrients.