Observations on obese patients eating isocaloric reducing diets with varying proportions of carbohydrate

Management strategies for weight control. Eating, exercise and behaviour

Obesity is a major health and social problem worldwide for which no single satisfactory treatment exists. Because of the prevalence of the disease, numerous therapeutic strategies have been attempted--often unsuccessfully. Weight loss programmes based on dietary restriction of caloric intake and nutritional education, exercise, surgical (gastroplasty, gastric bypass) and procedural (gastric balloon, waist cord, jaw wiring, liposuction) intervention and pharmacotherapy (appetite suppressants, thermogenic agents, bulking agents) used alone or in combination, have produced weight loss in the short to medium term; however, weight is generally regained on discontinuation of treatment. Behaviour modification programmes appear to offer the highest success rate in the long term. Weight loss is not rapid, although losses of 10 to 15 kg have been achieved after 6 months, and this may be increased when behaviour modification therapy is combined with more aggressive treatments such as severe caloric restriction or jaw wiring. Behaviour modification is particularly beneficial in special patient groups such as the obese elderly, children or adolescents, and disabled patients. Thus, although it appears that each of the treatments developed for the management of obese patients has its place, the cornerstone of therapy for most patients remains a programme of dietary restriction, combined with exercise and behaviour modification.

Obesity: basic considerations and clinical approaches

Obesity, defined as an excess of body fat, can be measured with a variety of techniques, but in most epidemiologic studies it is estimated from height and weight or from skinfold thickness. The "gold standard" for body fat is the body density from which fat and fat-free body mass can be calculated. The new technique of bioelectric impedance analysis may substantially improve the estimation of total body fat. For estimating regional fat distribution, either waist to hip circumference ratio or subscapular skinfold have been most useful. Using the body mass index, defined as weight in kilograms divided by the square of the height in meters (kilogram per square meter), the National Health and Nutrition Examination Survey estimated that 26%, or 34 million, adult Americans aged 20 to 75 were overweight. The prevalence of severe overweight (a body mass index above 30 kg/m2) is higher in the United States and Canada than in Great Britain, the Netherlands, or Australia. Obesity results from an increase in energy intake relative to expenditure. Total daily energy expenditure includes energy used during resting metabolism, energy associated with the ingestion of food, and energy needed for physical activity. The obese are often observed to be less active, but since carrying a heavier load requires more energy, their total energy expenditure may not be low. A low resting metabolic rate has been suggested as a predictor of future risk of becoming obese. Adipose tissue is the major site for fat storage and may contain more than 90% of total energy stores. The increase in body mass index or degree of body weight is associated with an increased risk of heart disease, hypertension, gall bladder disease, and diabetes mellitus. When fat is centrally located in either males or females, the risk for these diseases is also increased, and may be a more important risk factor than total overweight itself. Genetic factors form the background from which obesity develops. The best estimates suggest that these genetic factors may be of less importance than environmental events in determination of total body fat and its distribution. Obesity can be classified on the basis of the total number of fat cells and regional fat distribution by using the etiological factors which caused the obesity or by determining the age at which the obesity began. Regardless of the cause, treatment for obesity should be based on an evaluation of the individual's risk from obesity as compared with the risk of the treatment under consideration. (ABSTRACT TRUNCATED AT 400 WORDS)

Sucrose substitution in prevention and reversal of the fall in metabolic rate accompanying hypocaloric diets

Hypocaloric diets cause a fall in resting metabolic rate that interferes with weight loss. To evaluate the mechanisms underlying this phenomenon, resting metabolic rate was measured sequentially in six healthy obese women on a weight maintenance diet (more than 2,300 kilocalories), after 15 days of an 800 kilocalories carbohydrate-free diet, and after isocaloric sucrose replacement for an additional 15 days. The carbohydrate-free diet produced a 21 percent decline in resting metabolic rate (p less than 0.005) as well as a decrease in circulating triiodothyronine (41 percent, p less than 0.02) and insulin (38 percent, p less than 0.005) concentrations. Plasma norepinephrine levels also tended to decline (10 percent, 0.05 greater than p less than 0.1). However, when sucrose was substituted, resting metabolic rate rose toward baseline values even though total caloric intake was unchanged and weight loss continued. The sucrose-induced rise in resting metabolic rate was accompanied by a rise in serum triiodothyronine values, but not plasma insulin or norepinephrine concentrations. Throughout, changes in resting metabolic rate correlated with changes in serum triiodothyronine levels (r = 0.701, p less than 0.01). In four obese women, a hypocaloric sucrose diet was given at the outset for 15 days. The fall in both resting metabolic rate and triiodothyronine concentration was markedly reduced as compared with values during the carbohydrate-free diet. It is concluded that carbohydrate restriction plays an important role in mediating the fall in resting metabolic rate during hypocaloric feeding. This effect may, at least in part, be related to changes in circulating triiodothyronine levels. Incorporation of carbohydrate in diet regimens may, therefore, minimize the thermic adaptation to weight loss.