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Research has been conducted on the high-glycemic index carbohydrates. Results suggest that the consumption of these carbohydrates may increase hunger and promote overeating.

Research presented concerns the physiological aspects of unintentional weight loss in aging adults. Issues discussed concern biobehavioral and social factors that may impair the metabolism and regulation of food intake.

There remains controversy over the effect of age on postprandial thermogenesis, with some studies observing decreased postprandial thermogenesis in older subjects and other studies finding no effect of age. We investigated this issue in 8 young (25.2 [+ or -] 1.8 years) and 8 older (72.2 [+ or -] 2.1 years) healthy glucose-tolerant women with normal thyroid hormone status. Repeated measures of the thermic effect of feeding (TEF) were obtained following consumption of test meals containing 0, 1046, 2092, and 4184 kilojoules (kJ) by using indirect calorimetry. TEF at each meal size was determined once in the older subjects and twice in the younger subjects (during follicular and luteal phases of the menstrual cycle) for a total of 96 measurements. There was a positive dose-response between meal size and TEF (p < .001) that was not significantly affected by age group. The best single predictor of TEF expressed as a percentage of meal energy content was waist-to-hip ratio ([R.sup.2] = .416, p < .02). These results indicate that aging is not associated with decreased TEF in the absence of factors such as a hypothyroid state or glucose intolerance.

Information on the macronutrient composition of the diet is needed in doubly labeled water studies to convert measured rates of carbon dioxide production into values for total energy expenditure. There is no general consensus, however, about the best method to determine food intake for this purpose. Four common methods of measuring food intake (7-day weighed food intake, 24-hour recall, and Fred Hutchinson Cancer Research Center/Block and Willett food frequency questionnaires) were tested for their ability to provide comparable food quotient and total energy expenditure data in doubly labeled water studies in 10 young and 10 older women. All methods gave mean values for total energy expenditure that were within 1% of each other. Individual values obtained using the 24-hour recall and food frequency questionnaires were within +3% (standard deviation) of values determined using data from the 7-day weighed food record. These results suggest that it is not necessary to use time-consuming and expensive 7-day food records in doubly labeled water studies; instead, food intake data obtained more easily by 24-hour recall or food frequency questionnaire can provide comparable data. J Am Diet Assoc. 1998; 98:1015-1020., The doubly labeled water method is an isotopic method for determination of total energy expenditure (TEE) in free-living subjects (1,2). The method is based on measurement of the differential rates [...]

Blood glucose regulation in the fasting and fed states has important implications for health. In addition, the ability to maintain normal blood glucose homeostasis may be an important determinant of an individual's capacity to regulate food intake. We tested the hypothesis that aging is associated with an impairment in the ability to maintain normal blood glucose homeostasis following the consumption of large meals but not small ones, a factor that could help to explain age-related impairments in the control of food intake and energy regulation. The subjects were eight healthy younger women (25 f [+ or -] years, SD) and eight healthy older women (72 [+ or -] 2 years) with normal body weight and glucose tolerance. Following a 36-h period when diet and physical activity were controlled, subjects consumed test meals containing 0, 1046, 2092, and 4184 kJ (simulating extended fasting, and consumption of a snack, a small meal, and a moderately large meal), with 35% of energy from fat, 48% from carbohydrate, and 17% from protein. Each subject consumed each of the test meals on a separate occasion. Serial blood samples were collected at baseline and during 5 h after consumption of the meals. Measurements were made of circulating glucose, insulin, glucagon, free fatty acids, and triglycerides. There was no significant difference between young and older women in their hormone and metabolite responses to fasting and consumption of the 1046-kJ meal However, following consumption of 2092 and 4148 kJ, older individuals showed exaggerated responses and a delayed return to premeal values for glucose (p = .023), insulin (p = .010), triglycerides (p = .023), and the ratio of insulin to glucagon (p = .026). In conclusion, these results suggest an impairment in the hormonal and metabolite responses to large meals in older women.

The effects of fat-modified foods or low-fat diets will only have a slight effect on obesity. Fat replacement or reductions are only one part of a broader scheme that must involve lifestyle modification. Consumers who use fat-modified foods consistently over many years may witness a impact toward recommended dietary goals.

Previous studies by our group and others have suggested that nutritional stunting may increase the risk of obesity. To investigate mechanisms that could explain a link between stunting and obesity, a 22-mo follow-up study was conducted in two groups of shantytowns school girls (7-11 y old) in Sao Paulo, Brazil. One group (n = 15) had mild stunting (defined using a cutoff of -1.4 Z-scores of height-for-age) but normal weight-for-height; the control group (n = 15) had normal weight and height. Similar energy intake, dietary macronutrient composition and energy expenditure were observed in the two groups. Both groups showed comparable levels of IGF-1 that were below the normal range. A significant and positive association between baseline IGF-1 and the change in height-for-age during follow-up was found in all subjects combined (P = 0.044). A significant association was found between the baseline percentage of dietary energy supplied by fat and the gain in weight-for-height during follow-up in girls with mild stunting (P = 0.048), but not in the nonstunted control girls (P = 0.245); however, the slopes of these relationships were not significantly different. This study raises the question of whether a diet high in fat may increase the susceptibility to excess body fat gain in children who are mildly stunted. Further studies are need to explore this issue and to examine the possible etiological role of low levels of IGF-1. KEY WORDS: stunting; malnutrition; obesity; body composition

Relatively little is known about the influence of age on energy regulation during energy imbalance. We compared the effects of underfeeding on changes in energy expenditure, substrate oxidation, and body energy loss between young men (age 22.0 [+ or -] 0.9 [SEM] years) and older men (age 66.0 [+ or -] 1.8) who were leading unrestricted lives. Changes in total energy expenditure (TEE), resting energy expenditure (REE), the thermic effect of feeding (TEF), respiratory quotient, and body energy loss were determined in response to undereating by 3.17 [+ or -] 0.16 Megajoule (MJ)/day for 21 days in 19 healthy subjects consuming a typical diet. No significant effects of age were observed in changes in TEE, REE, TEF, or body energy loss in response to underfeeding. Thus, older men do not appear to have any impairment of energy conservation during negative energy balance compared to young men. This normal pattern of energy conservation during undereating together with the previously demonstrated reduction in energy dissipation during overeating can be predicted to promote body fat deposition in older men during the cycles of positive and negative energy balance that occur during normal life. This finding may help to explain the increased body fat mass in older individuals.

Relatively little is known about the influence of age on energy regulation during energy imbalance. We compared the effects of overfeeding on changes in energy expenditure, substrate oxidation, and energy deposition between young men (age 23.7 [+ or -] 1.1 [SEM] years) and older men(age70.0 [+ or -] 7.0) of normal body weight who were leading unrestricted lives. Changes in total energy expenditure, resting energy expenditure (REE), the thermic effect of feeding (TEF), respiratory quotient(RQ), and body energy content were determined in response to overeating by 4.09 [+ or -] 0.07 Megajoule (MJ)/day for 21 days in 16 healthy subjects consuming a typical diet. After excluding data from one young subject with unusual results and adjusting for individual differences in excess energy intake, there was a tendency towards a smaller increase in REE in older men compared to the young men (p = .07) which was accounted for by their lower fat-free mass (p = .016). There was also a significantly smaller increase in resting energy expenditure averaged over fasting and fed states (i.e, REE [+ or -] TEF) with overfeeding in order men than in young men (p < .01). Combined, these smaller increases in energy expenditure with overfeeding in the older subjects averaged an estimated 365 kilojoule (kj)/day (8.9% of the excess energy intake) (p

Genetic abnormalities found in both animal and human research may contribute to obesity. Researchers have identified three obesity genes in mouse models, the agouti protein, the Ob protein, and the fat gene. In contrast, genetic evidence in human obesity seems to be much more complex. Possible contributing factors to total body fat include DNA variations of apolipoproteins, uncoupling protein, adrenergic receptors, and lipoprotein lipase. Five human genes may be linked to abdominal fat accumulations. Fat deposits in certain parts of the body has also been linked to DNA polymorphisms, such those for insulin, apolipoproteins, and adrenergic receptors.

Controversy continues on the role of energy expenditure in regulating energy in human beings. It has been seen that energy expenditure contributes to energy regulation in normal individuals and also to the deregulation of energy balance that distinguishes obesity. An apparent equilibration between physical activity and body fat content due to a direct influence of physical activity on the metabolic determinants of energy balance is also suggested.

Older men who overeat or undereat for a period of time may lose their ability to regulate caloric intake. Researchers studied 17 healthy men who were in their early 20s and 18 healthy men in their 70s. For a period of 21 days, seven young men and nine older men were overfed while 10 younger men and 9 older men were underfed. Changes in body composition, weight, and caloric intake were recorded during the over- or underfeeding period and 46 days subsequently. After the overfeeding period, young men ate less than their bodies required for weight maintenance and their body weight decreased rapidly. Older men, however, continued to exceed their body's caloric requirements for weight maintenance and they did not lose the weight gained during overfeeding. After underfeeding, young men ate more food than their bodies required for weight maintenance. At the end of the study, these men actually weighed more than they did at the study onset. After underfeeding, older men continued to consume fewer calories than their bodies required. They failed to regain their normal body weight by the end of the study., Objective. - To investigate the effects of aging on mechanisms of body energy regulation and thereby determine the causes of unexplained weight loss in older persons, a factor predisposing to premature death and disability. Design. - Dietary intervention study. Setting. - Metabolic ward and outpatient. Participants. - The subjects were 35 healthy younger and older men of normal body weight consuming a diet of typical composition and performing usual activities. Main Outcome Measures. - Subjects were either overfed by a mean ([+ or -] SD) of 4.09 ([+ or -] 0.26) MJ/d (n=17) or underfed by 3.17 ([+ or -] 0.68) MJ/d (n=18) for 21 days. Measurements were made of changes in body weight, body composition, and energy expenditure during overfeeding or underfeeding, and of subsequent voluntary nutrient intakes and changes in body weight. Results. - There was no significant effect of aging on changes in body composition, body weight, or energy expenditure with overfeeding or underfeeding. However, following overfeeding, younger men exhibited spontaneous hypophagia, whereas the older men did not (mean [[+ or -] SD] changes in energy intake relative to control values were -2.11 [[+ or -] 2.18] and 1.55 [[+ or -] 2.11] MJ/d, respectively; P=.006). As a result,the younger men lost the excess body weight gained during overfeeding but the older men did not. Similarly, following underfeeding, the younger men exhibited hyperphagia while the older men did not (mean [[+ or -] SD] changes in energy intake relative to control values were 1.88 [[+ or -] 2.31] and -0.52 [[+ or -] 1.54] MJ/d, respectively; P=.02), and as a result the older men failed to regain the weight lost during underfeeding. Conclusions. - These results in 35 men suggest that aging may be associated with a significant impairment in the ability to control food intake following overeating or undereating. since overeating and undereating occur routinely as part of the normal pattern of energy regulation, the findings reported herein may help to explain the vulnerability of older persons to unexplained weight gain and weight loss. (JAMA. 1994;272:1601-1606)

High-intensity resistance exercise training may improve the muscle strength and mass and decrease frailty in elderly people. In a study of 100 frail nursing home residents aged 72 to 98, an experimental group performed high-intensity progressive resistance exercises of the hip and knee muscles for 10 weeks and also consumed a nutritional supplement. Muscle strength measurements, including gait velocity, stair-climbing ability, and overall physical activity, improved in the experimental group, but not in a group performing placebo activities such as aerobic or flexibility exercises. The nutritional supplement was not found to have an effect, either positive or negative. The results of the study suggest that the musculoskeletal system of the elderly person can overcome previous disuse when challenged by resistance training, and can realize significant improvement in mobility and overall activity.

We investigated the importance of adaptive variations in energy expenditure in the regulation of energy balance in young and elderly men of normal body weight leading unrestricted lives. Changes were measured in total and resting energy expenditure and body composition in response to overeating by approximately 4.2 MJ/d or undereating by 3.3 MJ/d for 21 d in 39 young and elderly men consuming a typical diet. In the young men, an average of 85-90% of the excess energy intake during overeating was deposited. During underfeeding, mobilization of body energy compensated for an average of 65% of the energy deficit in these subjects. The resting metabolic rate, averaged for fasting and fed states, increased during overfeeding (+0.63 plus or minus 0.20 MJ/d, P < 0.01) and decreased during underfeeding (-0.42 plus or minus 0.12 MJ/d), but at least some of these changes were due to the obligatory expenditure associated with nutrient assimilation. There was no significant change in energy expenditure for physical activity or thermoregulation from overfeeding or underfeeding. Preliminary results indicate that aging had no effect on responses to overfeeding or underfeeding. These findings suggest that adaptive variations in energy expenditure are not the major determinant of energy regulation in young adults of normal body weight and that, instead, energy balance is maintained on a day-to-day basis through the control of nutrient intakes.