The higher the normal body temperature of any species the longer will the average life span of its members be, but the lower the average body temperature of an individual member of that species the greater will that individual's life expectancy be. Body temperature reflects metabolic rate (the amount of food burned per day per unit of body weight). The lower the metabolic rate the greater the life span, and the higher the metabolic rate the shorter the life span.
In our quest for life extension, therefore, reduction of our personal metabolic activity rate and our core temperature would seem to be highly desirable objectives.
Dietary restriction offers one method of achieving all these objectives, but there may be other methods which can help. In a recent major review of life extension research, the international magazine Newsweek induded discussion of evidence relating to the use of meditation techniques:
A mellow state of mind acts on the body as well as the brain . . . a study reported last year  found that when 73 residents (average age 81) of old-age homes were randomly assigned to groups which either practiced transcendental meditation relaxation, or nothing, the meditation group showed the greatest improvement in blood pressure, memory and survival.
'Search for the Fountain of Youth' by Sharon Begley and Mary Hager (Newsweek, 5 March 1990, pages 34 8)
Why should meditation lengthen life? Perhaps because one of its influences involves a slowing down of biological activity. Remember the thousands of mice in Little Rock described in Chapter 5? They received 40 per cent fewer calories than normal laboratory mice and lived twice as long! Mice are known to achieve amazing degrees of life extension, although quite clearly without the benefits of meditation techniques. Part of the physiological change seen in mice on dietary restriction is a reduction of their metabolic rates. Their internal biological activities were slowed down with the very real benefit of reducing free radical activity.
Whether slower metabolic processes (which equals lower body temperature and therefore reduced free radical activity) is achieved by dietary restriction (calorie reduction) or by meditation does not seem to matter at all and, as will be made clear in the section on strategies, a combination of both would seem to be highly desirable. Dietary restriction, however, does not always produce a lower metabolic rate (and lower body temperature).
Weindruch and Walford look at body temperature
It is not surprising that these two key researchers into ageing have also applied their minds to an understanding of the implications of altered body temperatures. In 1979 they were the first to report a major decrease in internal body temperature in mice kept on a dietary (calorie) restriction programme which led to an increased life span. Those mice which were long-lived showed between 1.2 and 2.5°C lower core temperature than did the shorter-lived, fully fed mice. (AU mice had their temperatures taken, rectally, each morning. Weindruch and Walford comment on the displeasure and possible increase in body temperature this produced in them, and suggested that a surgical implant which allows temperature to be monitored without repeated handling of the mice to be a better method!)
They also report on a study conducted by others which confirms these findings. Here life extension was clearly demonstrated in mice receiving 75 per cent of their normal diet, while the core temperature recorded in these animals was 1.5°C lower than fully fed, control animals which did not achieve life extension. The drop in core body temperature is not only seen in 'normal' mice, but is observed to be more strongly evident in genetically overweight mice following a dietary restriction programme.