© Leon Chaitow, N.D., D.O.

Is it safe for humans?
Only a few years ago, despite having a deep knowledge of the effectiveness of dietary restriction on life extension, some experts seemed reluctant to believe that this sort of approach could be applied to humans. For example, in his major work Secrets of Life Extension (Harbor, San Francisco, 1980) John Mann states:

At present there is no safe way to apply the calorie restriction techniques towards the extension of human life. They would have to be started shortly after weaning and continued thirty years or more. The mortality rate would be high, and if a person did survive, his mental, emotional, and social development would be distorted by the drastic experience.

So John Mann, as recently as 1980, felt obliged to warn off seekers of a longer life span with this categorical statement that while these methods were OK for fruit flies and mice, there was no way humans were going to be able to benefit from the knowledge by applying modified versions to themselves.

And yet less than a decade later Drs Weindruch and Walford came to a vastly different opinion; that life extension through dietary modification is not only possible but safe. They arrived at this conclusion largely from having successfully conducted a lengthy series of dietary interventions involving adult animals, where, by skillful and slow introduction of dietary restriction, they have avoided the hazards which Mann seemed to believe were automatically built in to the process (and which might well be if early intervention is attempted, before maturity?.

Cautions
A first and vital caution is therefore that dietary restriction techniques should never be applied to children. In this context a child is someone who has not yet completed growth, and for safety's sake this rule should apply to anyone under 20 years of age. This ban, however, does not apply to periodic therapeutic fasting or to the use of antioxidant nutritional strategies, but it certainly does apply to the methods of caloric restriction which I describe later in this part of the book.

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.

Evidence abounds of an adult human's ability to withstand lengthy periods of caloric and general dietary restriction (starvation) for periods of up to two months, as long as liquids are available. If supplements are provided, starvation (restriction of food involving not only calories but all nutrients) for up to six months is possible (depending on available body tissues) without serious long-term effects. However, similar (or even much shorter) periods of dietary restriction involving children would produce marked malnutrition, and probable irreversible stunting and damage to immune and other functions. So, on no account must this be tried.

Weindruch and Walford state: 'Restriction beginning about 20 years of age in humans would, in our view, be free of potential childhood drawbacks, yet afford the greatest extension of life span consistent with safety.' This view is one this book supports, and upon which many of its recommendations are based. It is, however, not a recommendation for anyone to apply dietary restriction methods to themselves or their family. Any personal experimentation is taken to be at own risk, with careful consideration of current state of health, and after discussion with a suitably qualified health professional taking account of the advice and cautions given in this book.

Is it ever too late to start?
Not according to an experiment conducted in 1955 involving 60 people of average age 72, living in a religious institution for the elderly. AU were healthy and none was under the age of 65 at the outset (E. Vallejo, Review of Clinical Experiments (1957) 63:25). The diet which the experimental group received contained a well balanced and fairly hearty 2,300 calories on odd days of the month, with a drastic reduction on even days, on which they received one liter of milk and around 11b of fresh fruit (hardly an ideal restriction pattern, but adequate for experimental purposes). Sixty other people at the institution continued to receive the 2,300 calorie diet daily throughout the study so that they could be compared with the experimental group. The study lasted for three years, during which time those on the restricted diet spent a total of 123 days in the infirmary compared with a total of 219 days for the full-diet group, and only six of the dietary restriction group died as against 13 of the full diet group.

These results suggest that it is not too late to reap benefits by starting dietary restriction strategies, even moderate ones, fairly late in life. Animal studies confirm that middle and advanced age interventions produce significant benefits in life extension and health terms, if 'undernutrition without malnutrition' methods are applied correctly.

Don't start too quickly or cut the diet too much!
The keys to the successful achievement of life extension, when dietary restriction is applied to middle aged and elderly animals, lie in: (a) the speed with which the introduction of the regime is achieved, and (b) the degree of severity of the dietary regime. In early studies, involving dietary restriction of adult animals, results had been poor (hence Mann's negative opinion about applying it to humans) because the dietary changes were made too rapidly or the regime itself was too severe. Once Weindruch and Walford realized that adult animals would respond well by staying healthy and living longer if calorie reductions were made slowly and the reduction in calorie intake was not too drastic, compared with previous intake, results began to improve and life extension was achieved with regularity.

As a general guideline, then, 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. I give guidelines in the next chapter for what might be attempted at different ages.

How can you know if the diet is too severe?
Weindruch and Walford discuss the amazing way in which animals will adapt to dietary change. In general, if calorie intake is increased, their metabolic rate rises and they become less 'efficient' in their use of energy, a tactic which allows them to retain their normal body weight. When calorie intake is reduced they become more efficient in their use of energy, and again tend to retain their body weight at around their individual normal level. This is a phenomenon which glimmers have had to contend with to their eternal frustration.

Within any group of animals or people there are known to be wide variations in the degree of metabolic efficiency, with some maintaining their normal body weight whilst eating twice the quantity of another. This individuality factor makes it difficult to give specific recommendations of quantities to be eaten, and causes guidelines to be at best vague. We have what scientists term a 'set point, which is the weight our body tries to maintain, whatever the dietary pattern, whether this involves increased or decreased calorie intake.

Weindruch and Walford suggest that 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 in the subject's own set point.

How can we know what our 'set point' is?
According to Weindruch and Walford:

The set point for individuals whose body weight has been stable since ages 20 to 30 is precisely that body weight. For those who have gradually gained body weight with age, the appropriate set point in terms of dietary restriction regimen is uncertain.

Clear guidelines

1. If your weight has remained stable since your 20s you need to ensure that any dietary intervention you decide to adopt, using calorie restriction with full nutrition, achieves not less than a 10 per cent and not more than a 25 per cent reduction from your normal weight.

2. If you have gained weight steadily since your 20s the reduction you need to aim for, should you decide to apply this dietary approach, is one which takes your body weight to a level which is not less than 10 per cent and not more than 25 per cent below the average weight you were when in your 20s.

What are your energy needs?
A further consideration is also necessary: how efficient is your use of energy? Evidence of wide variations in calorie intake exist between people of the same size and weight, efficiently performing much the same rate of work. Even an individual's own energy requirement may vary from time to time by fairly wide degrees (up to 30 per cent higher or lower requirement of energy-based food) for no apparent reason, and with no apparent ill-effects in terms of weight change or functional ability.

A number of human studies have shown that energy requirement adapts to the diet being followed. Research reported on by Weindruch and Walford confirms that a steady reduction in intake of calories produces a lowering of metabolic activity (and therefore of required energy from food) which tends to stabilize when the right level of food intake is achieved to allow for the sort of weight loss described above. What the calorie intake should be really needs individual assessment, they maintain, but nevertheless they do give broad guidelines: 'It seems probable that for a US population [it would be no different in the UK], a daily intake of around 1,800 to 2,000 calories would induce a very gradual body weight loss which we surmise to be the best procedure.'

They suggest that an average individual would adapt in this way, and that once body weight loss of 10 to 25 per cent (from 'set point' weight) had been achieved, there would be no further loss of weight on a calorie-restricted pattern involving 1,800 calories per day. On such a diet there should be no ill-effects such as tiredness, apathy, weakness or swellings, all of which would indicate the likelihood of nutritional deficiencies in the diet, something which clearly should be avoided if and when calorie restriction is introduced.

Maintaining nutrient levels
It is absolutely essential for the mineral and vitamin content of the diet to be maintained, and because this is something which only a few people would be able to work out for themselves from their dietary intake, it is suggested and strongly urged, that anyone applying calorie restriction methods should supplement daily with a broad based multi mineral and multivitamin tablet/capsule containing all essential nutrients in quantities which ensure that RDA levels are achieved. The restricted diet, producing around 2,000 calories daily, should include enough protein to provide between 0.8 and 1.0 gram of good quality protein per day for each kilogram of body weight. The diet should not contain less than 0.4 and not more than 0.6 grams of fat per day per kilogram of body weight.

Will you be hungry all the time?
It is now a well-established phenomenon that when food is nutritionally sound, less of it is eaten without any sense of hunger being noticed. Satisfaction (satiety), a feeling of having 'had enough' comes sooner (after less food is eaten) in both humans and animals when nutritionally excellent meals are provided compared with the amount eaten when 'cafeteria' type food is eaten. When such 'tasty toxins' (lots of 'empty' calories food with no nutritional value) are a major part of the diet greater consumption follows and greater heat production (metabolic rate) is the result.

In one human study, lasting for five days, those involved were allowed to eat until they had had enough (reached satiety) of two different diets, one of which provided a high calorie content but low nutritional value, and the other high nutritional value and low calorie content. The results were that satiety was reached after only 1,570 calories had been consumed of the nutritious diet, whereas 'enough' was only reached with 3,000 calories of 'empty' food.

The aim in the recommended diet patterns in the next chapter is to offer nutritionally dense foods, with as few empty calories as possible. In this way feelings of hunger and desire to snack or nibble will be avoided.

Are there any dangers in dietary restriction methods?

1. The concept that life extension will only be achieved if these methods are introduced in infancy, and that such efforts would produce widespread damage and possibly death are now totally disproved. Nevertheless, to repeat the warning, no attempt should be made, without medical supervision, to use dietary restriction approaches on children.

2. Negative results were seen in early animal studies because the methods were incorrectly applied, with too drastic a cut in food intake, frequently of unbalanced foods. When correct feeding of nutrients is ensured, and the methods are applied at the right speed, no danger exists. Successful application to adult animals, and human experience, has given us clear guidelines for the best methods. It is, therefore, necessary to ensure that weight loss is not too rapid, say no more than 21b (approx 1 kilo) per week at most until the ideal weight (see items 6 and 7 below) is reached, at which time a stable weight should be achieved despite the continued restricted diet.

3. Nutritional deficiency is widespread even on a full so-called balanced diet in the US, UK and most industrialized societies. Evidence for this is based on a catalog of studies involving hundreds of thousands of children, teenagers, young adults, the middle-aged and people in retirement homes, ranging from the affluent to the very poor, all of which show that about half the populations of North America and Europe are deficient in one or more important nutrient (with many deficient in more than one). Those most commonly found to be too low for optimal health are zinc, vitamin E, riboflavin*, folic acid*, vitamin A, vitamin B6*, thiamine* and vitamin C (those marked with an asterisk are part of the vitamin B-complex). All of these are either antioxidants themselves (vitamins A, C and E) or are involved with enzyme and other antioxidant activity, making the avoidance of such deficiencies all the more important for life extension purposes. If nothing more was done, in trying to implement calorie restriction, other than a reduction in the amount of what is currently being eaten, such deficiencies would simply be made worse. It is essential, therefore, that any attempt at dietary restriction should be accompanied by nutritional supplementation and not just involve a cut in regular eating habits.

4. It is well known that dietary restriction can delay puberty, which is one of the reasons for setting the limit for starting such a programme at age 20 or later. It is also well established that dietary (calorie) restriction may result in a delay in menopause when early restriction patterns have been adopted. In animals the method leads to a lower degree of fertility but this is rapidly reversed, when full feeding is once more started. This can be compared with a common phenomenon seen in women athletes who stop ovulating and menstruating when their levels of body fat are reduced to below 15 per cent of their total weight. This is also seen to happen with girls suffering anorexia nervosa. According to Weindruch and Walford: 'Dietary restriction might in fact be made to act as a birth control measure, at the same time prolonging the time of the child-bearing age' Anyone who is pregnant or who plans on becoming pregnant should take account of this knowledge and avoid or postpone application of dietary restriction accordingly.

5. Although it might be imagined that dietary restriction would encourage osteoporosis in women, the reverse is thought to be likely. Studies involving animals and humans (vegetarians, for example) indicate that bone metabolism becomes 'younger' with dietary restriction, and as a consequence calcium levels should be maintained at a better level. Weindruch and Walford nevertheless suggest that bone metabolism be monitored during dietary restriction in postmenopausal women.

Additional benefits of dietary restriction
The health benefits which dietary restriction should produce make it a compelling choice, even if the life extension benefits are not 100 per cent guaranteed. The major health benefit would seem to lie in prevention of age-related disease of all types. Areas where benefits might be anticipated, if such diseases already exist (based on human and animal experience), include cancer, hypertension, diabetes, cardiovascular disease, auto immune diseases (such as rheumatoid arthritis), kidney disease and infertility.

Anyone suffering from any disease should be aware that dietary restriction applied to their condition should be monitored by an expert in nutrition and health. The conditions listed are not suitable for self-treatment, nor is this in any way recommended.

Conclusion
As we move towards a description of ideal eating patterns for dietary restriction we should remind ourselves of the enormous effort which has been put into uncovering the truths which lie behind the evidence. Credit needs to go to a host of researchers, in particular Drs Weindruch and Walford, whose work has been so extensively referred to in this book.

Among their conclusions are:

The overall probability that dietary restriction will retard human ageing and exert widespread favorable effects on health and function, is as great as the efficacy of many preventative and therapeutic measures which orthodox medicine currently recommends.

What these scientists have done, in effect, is to prove that the methods naturopaths use (and which they pioneered in Germany, the USA and UK) are safe and effective. These have always been seen to be preventive when started early in adult life, and to offer hope for chronic (age-related) diseases. What naturopaths did not know was that their methods would hold out the chance of an extension of life itself. If this is true, as all the evidence suggests, then we have for the first time, well tried naturopathic methods, supported by the research of scientists of international repute, which might well result in a true revolution in medical thinking.

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.