Calorie Restriction 

Such a practice is well documented to lead to improvements in a wide variety of measures of health - and following a calorie restricted diet is also currently the best-established and most clearly scientifically supported life-extension intervention in a wide range of species.

The energy deficit causes a loss of many types of body tissue.

As a result of adaptations designed to deal with low food conditions, the body changes into a different gear - a state where there is more of an emphasis on self-preservation than on reproduction.

This shift of priorities manifests itself as improved bodily health, and a reduced rate of mortality and age related decline.

The phenomenon has been studied by scientists since then.

Today, CR is the most effective and reproducible intervention for increasing lifespan in a wide range of animal species.

It has been found to extend lifespans in protozoa, yeasts, rotifers, water fleas, flies, spiders, worms, fish, mice, rats, hamsters, dogs and cows - and to reduce mortality in squirrel monkeys and rhesus monkeys.

CR is also the most potent, broadly acting cancer-prevention intervention.

In practice - for most people - adopting a CR diet can mean some changes to what they eat - as well as reducing how much food they consume.

• What to eat 
  
  Many CR practitioners will find themselves eating more things from the first column - and less things from the second:

  Eat much more	Eat much less
  Green vegetables Salad fruit Berries	Cakes Biscuits Sweets
  Eat a bit more	Eat a bit less
  Root vegetables Fruit Fish Nuts Seeds	Cereals Bread Potatos Meat and dairy Crispbread

  By exchanging high-calorie/low-nutrient foods for low- calorie/high--nutrient ones, it becomes possible to reduce the net caloric intake - without eating any fewer nutrients.

• Example meal 
  

  Typical meal	Restricted meal
  Calories: 1268 From fat: 33% From protein: 22% From carbohydrates: 45%	Calories: 750 From fat: 10% From protein: 25% From carbohydrates: 65%

• Supplements 

  Some practitioners also use dietary supplements. These contain nutrients and are very low in calories - but can have their share of drawbacks.

  Getting nutrients from food seems to be preferrable where possible.

• Satieity 

  Some practitioners report that they feel hunger more than they used to. Others seem to become accustomed to the CR state - and find it effortless to maintain after a while.

  The volume of food consumed prectitioners consume may not necessarily be reduced overall. Eating lots of fibrous raw vegetables is one way in which people practice CR.

  Such bulk usually has the effect of keeping one of the body's satiation mechainsms satisfied - and helps prevent feelings of hunger - by persuading sensors in the stomach and digestive system that the body is full of food.