by Ben Best
For a person who is neither gaining nor losing weight, the calories being consumed will equal the sum of calories burned & excreted. It follows that for a person who chooses to reduce calorie intake, a weight loss will occur until a new equilibrium position is reached in which calorie intake again equals calorie consumption/elimination.
Individuals with a larger body mass naturally require more energy to maintain that mass. However the calorie-burning effect of a larger body mass is not simply linear, because overweight individuals also have an elevated metabolic rate. For each kilogram of weight lost, metabolic rate has been seen to drop by 20 calories per day [AMERICAN JOURNAL OF CLINICAL NUTRITION 45:1035-1036 (1987)].
Among obese persons trying to lose weight, only about 20% are able to lose at least 10% of initial body weight and keep it off for at least one year. Frequent self-monitoring of weight, physical exercise, and low fat diets are predictors of sucess [ANNUAL REVIEW OF NUTRITION; Wing,RR; 21:323-341 (2001)]. To pursue a low fat diet in practicing CRAN, care should be taken not to eliminate essential fatty acids. (See Fats You Need)
Thus, a person beginning a program of Caloric Restriction with Adequate Nutrition (CRAN) should plan for a period of weight loss. CRAN practitioners will either target a new weight or a new level of daily caloric intake, but neither the choice of a target nor the route to the target are obvious. The questions arise: how much weight loss should occur and how rapidly should the weight loss occur? It is impossible to answer these questions with any precision using current scientific knowledge. People vary greatly in initial weight, age, height, health status and bone structure. For a given weight, a person with heavy bone structure will have less muscle&fat than a person of light frame. People of the same weight, height & frame will have a different distribution of lean & fat tissue.
More fundamentally, it has not currently been proven that CRAN extends the lifespan of humans, much less what the optimal CRAN or transition to CRAN is for any specific individual. The best we can expect from current scientific knowledge is information on avoiding the detrimental effects often seen with weight loss.
Some CRAN practitioners attempt to trivialize the significance of Adequate Nutrition in Caloric Restriction, but the most knowledgeable researchers in the field rarely speak of restricting calories without emphasizing the importance of sufficient nutrient. Dr. Walford has used the phrase "high/low diet", but never "low diet". There is a good reason for this, not the least of which is the fact that a significant proportion of researchers prior to 1970 failed to properly demonstrate the life-extending properties of Caloric Restriction due to insufficient attention to Adequate Nutrition. Even today, many otherwise-capable scientists still equate CRAN with "starvation". And if scientists do this, what can be expected of the general public?
I am strident about this point not because it is a marketing issue, but because it is an issue of public health. It is known that a majority of those afflicted with anorexia nervosa are young women of high intelligence, yet the damage these women do to themselves is invariably associated with inadequate nutrition. I believe that if interest in CRAN continues to grow in the general public, then there will be increasing numbers of people attempting to practice it. Under these conditions it is socially irresponsible to risk the health & lives of would-be emulators by not emphasizing with every reference that Caloric Restriction MUST be practiced with ADEQUATE NUTRITION.
Moreover, although researchers have demonstrated that Caloric Restriction extends maximum lifespan when Adequate Nutrition is given to prevent deficiency disease, I have doubts that sufficient attention has been given to the nutritional requirements of weight loss. Adequate Nutrition during weight loss is not the same as Adequate Nutrition during steady-state Caloric Restriction. And since adult-onset CRAN invariably results in weight loss, insufficient attention to these additional nutritional requirements — even in experiments performed with laboratory animals — may mean that we are still ignorant of the full potential benefits and hazards of adult-onset CRAN.
Weight loss typically means a loss of both fat and lean tissue. The relative proportion of fat and lean loss are most significantly determined by (1) the initial body composition of the subject and (2) whether Caloric Restriction is in an initial or a long-term stage. Concerning (1), lean individuals lose proportionately more lean tissue and obese individuals lose proportionately more fat. A fasting obese person (overweight by more than 50 kilograms — 110 pounds) will show a 10 gram/kg nitrogen loss compared to a 20 gram/kg nitrogen loss for a fasting normal (nonobese) person. [AMERICAN JOURNAL OF CLINICAL NUTRITION 32:1570-1574 (1979)]. Moreover for a given rate of Caloric Restriction, lean individuals lose weight more rapidly than obese individuals. (This stands to reason, since at 9 calories per gram, a pound of fat represents about 4,000 calories — in contrast to a pound of protein which would be about 2,000 calories at 4 calories per gram.)
Concerning (2), under conditions of high Caloric Restriction of long duration, after the first week the weight loss in obese individuals will be 10% protein, 40% fat and 50% water, whereas after the first month (and thereafter) something closer to 10% protein, 70% fat and 20% water is seen [ANNUAL REVIEW OF NUTRITION 7:465-484 (1987)]. Not surprisingly, the rate of weight loss during the initial stages of very low calorie diets is much higher than in the later stage. Losses of potassium & sodium are particularly high during the initial state, as is nitrogen loss. Muscle is high in potassium, which is why anorexic patients with severe lean-tissue loss often show potassium depletion [HUMAN BODY COMPOSITION, A.Riche, S.Heymsfield & T.Lohman, Editors (1996), p.275-283 ]. Potassium is the only electrolyte which has been shown to have a clinically significant effect on arrhythmias [CIRCULATION 42:408-419 (1973)].
Loss of lean tissue does not spare the heart. Left ventricular mass of anorexic patients has been seen to be between one-half and two thirds that of age/sex-matched normal subjects [CIRCULATION 72:991-1000 (1985)]. Ventricular arrhythmias are frequently associated with these heart-tissue losses [CIRCULATION 58:425-433 (1978)].
Attempts have been made to treat life-threatening extreme obesity with zero-calorie diets, supplemented with vitamins&minerals. Too often this has resulted in death due to heart disease, as in the case of a 20-year old woman on a medically-supervised zero-calorie diet for 30 weeks who died of ventricular fibrillation. Her ECGs showed the depressed QRS voltage and prolonged Q-T intervals (in association with normal electrolyte levels) often seen in anorexics. Histological autopsy revealed gross myocardial fiber loss & fragmentation [THE LANCET 1:914-916 (1969)].
In 1976 a book entitled THE LAST CHANCE DIET popularized the idea of a calorie-restricted (300-400 calories/day) obesity-treatment diet supplemented with liquid protein to counteract the effects of nitrogen loss. A scholarly review of the history of this "fad" can be found in the book MANAGEMENT OF OBESITY BY SEVERE CALORIC RESTRICTION by B.Blackman & G.Bray (1985). Seventeen individuals died of ventricular fibrillations as a result of the program. Where data was available, these individuals showed the classic pattern of ECG voltage with prolonged QT interval & myocardial damage [AMERICAN JOURNAL OF CLINICAL NUTRITION 34:453-461 (1981) and CIRCULATION 60:1401-1412 (1979)]. Only 4 of the cases showed lowered blood potassium [AMERICAN JOURNAL OF CLINICAL NUTRITION 45:1126-1134 (1987)]. Interestingly, there was a linear correlation between initial BMI and time-to-death on the Very Low Calorie diet [AMERICAN JOURNAL OF CLINICAL NUTRITION 39:695-701 (1984)]. Dogs placed on a hypocaloric, micronutrient-supplemented, protein-poor diet have shown similar damage to the heart myofibrils [AMERICAN HEART JOURNAL 97:733-744 (1979)].
The exact cause of death for the 17 individuals on the Very Low Calorie (VLC) diet has never been proven, but it is suspected that the poor quality of the protein (collagen, often supplemented with tryptophan) was responsible. Modern VLC diets use protein of high biological value (often egg albumin) and carbohydrate to reduce ketosis & electrolyte loss (although the inclusion of carbohydrate often leads to intense hunger & increased difficulty complying with the diet) [INTERNATIONAL JOURNAL OF OBESITY 13(Suppl.2):1-9 (1989)]. A review of these modern VLC (800 calories/day) diets in the JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION stated that the mortality of the VLC dieters was actually lower than that of obese controls [JAMA 270:967-974 (1993)]. The greatest risk from weight loss with Adequate Nutrition is from gallstone formation, which dramatically increases for weight losses in excess of 1.5% of body weight per week for obese persons with an initial body weight in excess of 100 kilograms (220 pounds) [THE AMERICAN JOURNAL OF MEDICINE 98:115-117 (1995)]. Other reported side-effects of VLC diets include orthostatic hypotension, cold intolerance, constipation/diarrhea, anemia, menstrual irregularities and a tendency to sleep longer [ANNUAL REVIEW OF NUTRITION 7:465-484 (1987)].
Much of what has been learned about the hazards of weight loss has been learned either from those who fail to receive Adequate Nutrition (starving people, patients with wasting diseases and most anorexics) or medically-supervised obese dieters. Non-obese persons are less prone to gallstone formation. For the non-obese, it seems likely that loss of muscle mass & bone density are of most concern — and these can be reduced with exercise [AMERICAN JOURNAL OF CLINICAL NUTRITION 40:865-872 (1984)]. Weight loss by overweight persons is associated with increased mortality, but not for many of those who become or remain physically active [INTERNATIONAL JOURNAL OF OBESITY; Ostergaard,JN; 34(4):760-769 (2010)].
A study of dieting done on Boston Police Officers showed a 36% loss of lean tissue among the non-exercising dieters, compared with a 4% lean tissue loss among the exercisers. Although the groups received 800 calories per day, the exercisers lost 11.8 kilograms (26 pounds) while the non-exercisers lost 9.2 kilograms (20 pounds) [MEDICINE AND SCIENCE IN SPORTS AND EXERCISE 17:466-471 (1985)]. A study on exercising obese women demonstrated that the additional energy expenditure of exercise was not completely compensated-for by increased calorie-intake [AMERICAN JOURNAL OF CLINICAL NUTRITION 36:478-484 (1982)]. Exercise promotes an increase in cardiac muscle mass, capillary density and capillary/muscle-fiber ratios which can combat the danger of myocardial-fiber loss associated with lean-tissue loss [PROGRESS IN CARDIOVASCULAR DISEASES 57:297-324 (1985)].
Exercise can also have benefits in addition to those associated with loss of muscle & bone. CRAN without exercise lowers HDL-cholesterol without lowering LDL-cholesterol, whereas CRAN with exercise lowers LDL-cholesterol without lowering HDL-cholesterol [AMERICAN JOURNAL OF CLINICAL NUTRITION 33:1002-1009 (1980)]. These benefits may be responsible for the fact that in one study CRAN rats (30% calorie-restricted) that were exercised showed a 6% longer mean lifespan and a comparable maximum lifespan to unexercised CRAN rats [JOURNAL OF APPLIED PHYSIOLOGY 70:1529-1535 (1991)].
The benefits of weight loss for cardiovascular disease are well-known. The Framingham Heart Study showed that a 10% increase in weight results in a 6.5 mm Hg rise in systolic blood pressure [FOOD, NUTRITION & DIET THERAPY M.Krause & L.Mahan (1984) p.560]. Another study found a 3 mmHg and a 2 mmHg increase in systolic and diastolic pressure (respectively) for a 10 kg increase in body weight [CIRCULATION 39:403-421 (1969)]. A more recent meta-analysis found that a 4 kg weight loss through dieting was associated with a 6 mmHg reduction in systolic and a 3 mmHg reduction in diastolic blood pressure [ARCHIVES OF INTERNAL MEDICINE; Horvath,K; 168(6):571-580 (2008)].
Some people fear attempting to lose weight because of reports that weight-loss associated with subsequent weight-regain (especially repeatedly) can be more damaging to health than maintenance of the higher weight. For nonsmokers, this has been shown to be untrue [NEW ENGLAND JOURNAL OF MEDICINE 333:686-692 (1995)]. A major review of the literature concludes that there should be no concern by an obese person over the hazards of "Weight Cycling", although it did not make the same recommendation for non-obese persons [JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION 272:1196-1202 (1994)]. I suspect that insufficient data on dieting by non-obese persons and medical conservatism are the basis for this caution for the non-obese. And I think since the greatest risk for the non-obese is loss of lean tissue (especially heart tissue), that exercise can provide the proper protection against harm.
I have attempted to call attention to the fact that the Adequate
Nutrition of CRAN may be insufficient for the Adequate Nutrition required
for weight loss. Every person initiating a CRAN program will face this
problem because reduced daily calories will result in loss of weight until
a new steady-state is attained. It is not my purpose to — and I
specifically refuse to — say how much weight any given CRAN practitioner
should lose, or how fast they should lose it. However, it is my hope that
this review will provide guidelines which can be of use to others in
planning their own individual programs.