Scientific Reducing

RED U C IN G takes time and effort, so it should be properly planned. With only common sense, some understanding of the calorie value of foods, and the information given in the previous chapter, it is possible to reduce successfully. But a scientific programme adjusted to the needs of the individual, is safer, surer, and more efficient.

You can devise your own programme of scientific reducing, merely obtaining medical advice as to advisability and a little help if you have questions about the computations. Developing your own reducing programme is psychologically important and assures that you will be fully aware of what is involved in carrying out the programme. The section following, Body Calories and Their Expenditure, explains the scientific basis for your programme, and a later section, Practical Reducing Programmes, shows how to apply them.

To start with, it is necessary to decide how much weight should be lost; then the problem is to discover how many calories in the diet will keep the weight constant and to estimate the diet change needed to cause the desired weight loss in a specified time. The amount of food calories that holds the present body weight constant, neither gaining nor losing, is the calorie balance. Eating less than this amount produces a calorie deficit, which is made up by burning body fat. The weight loss is proportional to the calorie deficit.

Body Calories and their Expenditure A pound of pure animal fat, including human body fat, represents about 4,100 calories, but adipose tissue, the form in which it accumulates in the body, averages 15 per cent water and about 5 per cent protein and other non-fat materials. This "blubber" you want to be rid of averages about 3,370 calories per pound.

Reducing by dieting is not exactly the same as having a surgeon cut out some of your fat deposits. When you change weight by changing the diet, what you lose is not merely adipose tissue. Your blood volume shrinks a little and there is a reduction in the tissues that one way or another "support" the adipose tissue. The final result is that a pound of body weight change corresponds to about 3,200 calories of energy stored in the body.

At this point it would be easy to make some assumptions and a few flourishes of arithmetic purporting to arrive at an accurate estimate of your present calorie expenditure from your height, weight, and occupation. We want to make it easy but we do not believe you can look up the basal metabolism corresponding to your height and weight in a table, add 50 per cent for "activity" (housewife or desk worker), and arrive at a very reliable estimate for your present calorie balance point. Even with a measurement of basal metabolism the computation is highly uncertain, as we shall see.

Moreover, the translation of food calories into body weight calories is not entirely straightforward when the body weight changes. A common error in such calculations is illustrated by the example of the extra slice of bread so popular with lecturers and writers of articles on the problem of obesity. The argument goes like this. Suppose you add a single slice of bread (65 calories) to your daily ration. In a year this adds up to 65 x 365 = 23,725 calories so, at 3,200 calories to the pound, you will gain 7.4 pounds. The joker in this example is revealed when you ask what will happen in 20 years. Obviously, you are supposed to gain 20 x 7.4 = 148 pounds, that is 102 stones!

What actually happens is that when you change your diet but otherwise keep your mode of life constant, your calorie expenditure tends to follow suit and your weight change turns out to be smaller than you would expect from an elementary calculation. As the new diet is continued, you approach and eventually reach a new balance point of no further weight change. This has been demonstrated time after time under rigidly controlled conditions and it is not hard to see why it must be so.

The Three Ways Of Spending Calories

Your calorie expenditure consists of three items: 1. Basal metabolism (the cost of merely resting quietly with an empty stomach); 2. Muscular activity, and 3. Specific dynamic action (the energy cost of digesting and using your food, which averages about 10 per cent of the calorie value of the food you eat). All three of these are changed, and they all change in the same direction, when you change your diet.

First, and most obvious, is the change in specific dynamic action (S.D.A.). If you are in balance at 2,500 calories, neither gaining nor losing weight, and go on a diet of 1,500 calories daily, your deficit is not 1,000 calories a day. When you were eating 2,500 calories daily about 250 calories went into S.D.A.; at 1,500 calories of food daily the S.D.A. is 150 and your deficit is 900, not 1,000, calories a day.

Next, consider physical activity. This accounts for anything from about 20 per cent to over 60 per cent of the total calorie expenditure, a fair average being perhaps 40 per cent for sedentary people who are candidates for weight reduction. Table 4 lists typical calorie costs for various activities.

TABLE 4CALORIES AND PHYSICAL ACTIVITY Relative hourly calorie cost of different activities, taking the calorie cost of average sleep as 100 per cent. These are rough average estimates for ordinary adults.

Calories as Activity % of Sleep Older works on the diet often give tables of the calorie needs of people in different occupations - so many calories for a housewife, so many for a carpenter, and so on. These are almost useless for the dieter because of the great variation between individuals and between the actual energy costs of different versions of the same job. Persons of the same sex, weight, and occupation may easily differ by over 500 calories a day in their calorie needs or balance points. It must be remembered that with a 40-hour week only 25 per cent of the week is taken up by the occupation. Moreover, progressive mechanization is greatly changing the cost of work on the job.

Most of the calories spent for physical activity go into the cost of moving the body (and its extremities). And the cost of moving the body depends on its weight, that is, the weight to be moved. If a 14-stone man walks up stairs to a vertical height of 100 feet, he does 196 x 100 = 19,600 foot-pounds of work. If he carries a 50-pound box up the stairs, he is lifting himself plus the box, so he does (196 + 50) x 100 = 24,600 foot-pounds, so even in carrying fairly heavy loads most of the energy cost is in moving the body.

Obviously, then, if the body weight is changed, the energy (calorie) cost of activity is changed. If the body weight drops 25 per cent, say from 14 stone to 10 stone 8 pounds, the calorie cost of a one-hour walk at three miles per hour is decreased by almost exactly 25 per cent. Activity that formerly cost the 14-stoner 1,000 calories amounts only to about 750 calories when the weight is 101 stone.

Finally, consider the basal metabolism. It, too, is reduced when the body size is reduced, not quite in simple proportion to the weight loss, but still by an appreciable amount. Let us take an average example. For a 35-year-old person who should weigh about 9 stone 4 pounds, but weighs 15 stone 10 pounds, a change in weight to 12 stone 12 pounds, or a loss of 40 pounds, caused a decrease in basal metabolism of the order of 200 to 240 calories a day. This must be allowed for in calculating the weight change to be expected from continuing the diet. A reasonable allowance is to subtract from your calorie deficit 50 to 60 calories per day for the basal metabolism change resulting from each 10 pounds of weight lost.

Incidentally, the basal metabolism values in the standard tables used by most doctors are now known to be too high by around 7 to 10 per cent. The tabular values reflect the apprehension and lack of relaxation of the hospital patient who, for the first time, is connected to a lot of strange apparatus and is told to relax and breathe normally.