As Doctors Weindruch and Walford put it: 'Significant extension of maximum life span, will create a new society, radically different from the present one, and in our view with many advantages.'

Summary of dietary restriction technique

1. Dietary restriction techniques should never be applied to children.

2. No attempt should be made to deliberately increase growth hormone production in any child, by any means at all, unless under the guidance of a medical expert.

3. Restriction beginning about 20 years of age in humans should be free of potential childhood drawbacks, yet afford the greatest extension of life span consistent with safety.

4. Don't start too quickly or cut the diet too much!

5. As a general guideline, the older a person is when starting a dietary restriction programme, the more slowly should the process be introduced and the less severe the degree of restriction aimed for.

6. The ideal weight loss to aim for when following a calorie restriction diet is one which causes not less than a 10 per cent, and not more than 25 per cent, reduction from your own 'set point' (the weight your body tries to maintain whatever the diet).

7. If weight has remained stable since your 20s, any dietary intervention needs to ensure not less than a 10 per cent and not more than a 25 per cent reduction from that normal weight.

8. If weight has been gained steadily since your 20s then the level of reduction to aim for is one which reduces body weight to not less than 10 per cent and not more than 25 per cent below the average weight in your 20s.

9. It seems probable that for a US population (UK would be no different), a daily intake of around 1,800 to 2,000 calories would induce a very gradual body weight loss.

10. An average individual would adapt so that once body weight loss of 10 to 25 per cent had been achieved, there would be no further loss of weight on a calorie restricted diet of 1,XOO calories per day.

11. Supplementation daily is necessary with a broad based multi mineral and multivitamin tablet/capsule containing all essential nutrients in quantities which ensure that RDA levels are achieved.

12. The aim in the recommended diet patterns in the next chapter will be to offer nutritionally dense foods, with as few empty calories as possible so that feelings of continuing hunger are avoided.

13. No-one who is pregnant or who plans on becoming pregnant in the near future should use dietary restriction methods. If there are fertility problems dietary restriction followed by a return to full diet could appreciably improve fertility. Guidance from a health professional is desirable in such a case.

14. In order to forestall any risk of osteoporosis an additional calcium and magnesium supplement is recommended for post-menopausal women adopting a dietary restriction regimen, especially if you are white and slim.

15. No-one with an eating disorder (anorexia nervosa, bulimia) or a serious disease (cancer, diabetes, coronary disease, auto immune disease) should apply dietary restriction methods without expert advice, and possibly supervision. This does not mean that dietary approaches cannot help such problems, indeed much evidence suggests that they can. What it does mean is that the safest way to begin to use dietary strategies would be after taking expert advice.

16. No-one who is suffering from a mental disorder requiring regular medication or anyone receiving hormonal (steroid) treatment should use dietary restriction without expert advice and supervision.