Roland L. Weinsier

Divergent trends in obesity and fat intake patterns: The american paradox

PURPOSE To compare recent changes in diet and physical activity with trends in body weight and obesity prevalence, using large survey studies representative of the US population. MATERIALS AND METHODS Secular-trends survey studies were made from databases of NHANES II and III, USDA Nationwide Food Consumption Survey, Behavioral Risk Factor Survey System, and Calorie Control Council Report providing data on obesity prevalence, body mass index, calorie and fat intake, exercise-related physical activity, and consumption of low-calorie food extracted from surveys for the adult US population and specific subgroups. RESULTS In the adult US population the prevalence of overweight rose from 25.4% from 1976 to 1980 to 33.3% from 1988 to 1991, a 31% increase. During the same period, average fat intake, adjusted for total calories, dropped from 41.0% to 36.6%, an 11% decrease. Average total daily calorie intake also tended to decrease, from 1,854 kcal to 1,785 kcal (-4%). Men and women had similar trends. Concurrently, there was a dramatic rise in the percentage of the US population consuming low-calorie products, from 19% of the population in 1978 to 76% in 1991. From 1986 to 1991 the prevalence of sedentary lifestyle represented almost 60% of the US population, with no change over time. CONCLUSIONS Reduced fat and calorie intake and frequent use of low-calorie food products have been associated with a paradoxical increase in the prevalence of obesity. These diverging trends suggest that there has been a dramatic decrease in total physical activity related energy expenditure. Efforts to increase the average Americans total exercise- and nonexercise-related physical activities may be essential for the prevention of obesity.

Total body fat does not influence maximal aerobic capacity

OBJECTIVE: The objective of this study was to examine the influence of body weight and body composition on aspects of aerobic fitness. Our hypothesis was that increased body weight, specifically increased fat mass (FM), would not limit VO2max relative to fat-free mass (FFM), but would reduce maximal and sub-maximal VO2max relative to body weight.DESIGN: We used data from two ongoing studies. In Study 1 a cross-sectional analysis of 129 children across a wide spectrum of body composition was performed. In Study 2 we examined data from 31 overweight women before and after weight loss.METHODS: VO2max was measured using a treadmill test. Sub-maximal aerobic capacity was evaluated with respiratory exchange ratio (RER), heart-rate (HR), and oxygen uptake relative to VO2max at a given workload (%VO2max). Body composition was assessed using dual energy X-ray absorptiometry (DXA) (Study 1) and a four-compartment model (Study 2).RESULTS: In Study 1, FFM was the strongest determinant of VO2max (r=0.87; P<0.0001). After adjusting for FFM, there was no significant influence of FM on VO2max. After separating children into lean and obese sub-groups, absolute VO2max was significantly higher in the obese (1.24±0.27 vs 1.56±0.40) and VO2max relative to body weight was significantly lower (44.2±3.2 vs 32.0±4.1 ml/(kg-min)), whereas there was no significant difference when expressed relative to FFM (57.9±5.8 vs 59.2±4.9 ml/(kgFFM-min)). Sub-maximal aerobic capacity was significantly lower in the obese children, as indicated by a higher HR and %VO2max; time to exhaustion was significantly lower in the obese children (15.3±2.9 vs 11.1±2.1 min). In Study 2, FFM was also the strongest determinant of VO2max before and after weight loss. The relationship between VO2max and FFM was identical before and after weight loss so that VO2max relative to FFM was identical before and after weight loss (43.8±4.9 vs 45.5±6.4 ml/(kgFFM-min)). However, sub-maximal aerobic capacity was lower in the obese state, as indicated by a significantly higher RER (0.85±0.06 vs 0.79±0.05), HR (124±14 vs 102±11 bpm), and %VO2max (44% vs 36%).CONCLUSION: The major influence of body weight on VO2max is explained by FFM; FM does not have any effect on VO2max. Fatness and excess body weight do not necessarily imply a reduced ability to maximally consume oxygen, but excess fatness does have a detrimental effect on submaximal aerobic capacity. Thus, fatness and VO2max should be considered independent entities.

Evaluation of the strength-size relationship in vivo using various muscle size indices.

PURPOSE It is well accepted that maximum strength is related to muscle size. The primary purpose of this study was to determine whether anthropometric or dual-energy x-ray absorptiometry (DEXA) estimates of muscle size were valid predictors of plantar flexor maximum voluntary contraction (MVC) strength and could be used in lieu of more sophisticated techniques (e.g., magnetic resonance imaging (MRI)). Additionally, we compared the relationship among MVC and three MRI-determined muscle size measures; anatomical (ACSA) and physiological (PCSA) cross-sectional areas; and muscle volume (VOLm). METHODS We measured plantar flexor MVC at 1.83 rad and various indices of muscle size: 1) body weight, 2) total body lean mass (LM) (DEXA), 3) lower leg LM (DEXA), 4) lower leg circumference, 5) estimated muscle+bone cross-sectional area (CSA) from circumference and calf skin-fold, 6) triceps surae ACSA, 7) triceps surae PCSA, and (8) triceps surae volume (VOLm), in 39 premenopausal women (mean +/- SD: 36 +/- 8 yr, 165 +/- 6 cm, and 65 +/- 9 kg). RESULTS Zero-order correlations showed significant (P < 0.05) associations between MVC and total body LM (r = 0.365), lower leg LM (r = 0.381), circumference (r = 0.584), estimated muscle+bone CSA (r = 0.447), ACSA (r = 0.733), PCSA (r = 0.715), and VOLm (r = 0.649). By using the Fisher Z-transformation, ACSA and PCSA correlated significantly higher with MVC (P < 0.05) than anthropometric and DEXA indices. Further, only ACSA and PCSA regressed to the origin, indicating the ability to predict MVC was greatest with these two measures. CONCLUSIONS The MRI-determined muscle size indices, which were specific to the triceps surae, correlated with strength better than whole limb anthropometric and DEXA indices. In this group of women, both ACSA and PCSA appeared superior to VOLm for predicting strength. PCSA was not found to be more precise than ACSA. ACSA appears to provide adequate precision for estimating plantar flexor specific tension in vivo.

Hospital-associated malnutrition: a reevaluation 12 years later.

A prospective evaluation of general medical patients at the University of Alabama at Birmingham was performed in 1976 and repeated in 1988 to determine change in malnutrition prevalence. Plasma folate, plasma ascorbate, weight for height, triceps skinfold, arm muscle circumference, lymphocyte count, albumin, and hematocrit measurements were combined to form a likelihood of malnutrition (LOM) score. The nutritional status of 228 consecutive patients was assessed by the LOM score at admission and at the 14th day of hospitalization and compared with 1976 findings. The same testing methods were used and the same patient diagnoses and demographic characteristics were found in 1988 and 1976. Of the patients staying more than 14 days, the length of stay was the same in 1988 and 1976 (30 days and 31 days, respectively). However, a smaller percentage of patients stayed 2 weeks or longer in 1988 (21% vs 33% in 1976). In 1988, high LOM scores at admission predicted longer lengths of stay and showed a trend toward increased mortality. The 1976 findings also showed that high LOM scores were associated with longer lengths of stay and increased mortality. LOM scores paired from admission to follow-up improved with stay in 1988 and worsened in 1976. The number of patients with high LOM scores at follow-up was lower in 1988 than in 1976 (46% and 62%, respectively). These findings indicate that identification of malnutrition indicators has improved since 1976. However, dietitians should continue to improve the nutrition assessment and intervention process.

The Effects of Strength Conditioning on Older Women's Ability to Perform Daily Tasks

OBJECTIVES: The objectives of this study were to determine the effects of a strength‐training program on walking speed and relative muscular stress, as measured by normalized integrated electromyographic (nIEMG) activity, while carrying a box of groceries and standing from a chair.

A role for high intensity exercise on energy balance and weight control.

The objective of this commentary is to remark on the impact, exercise intensity has on energy expenditure and its potential for body weight control. Exercise intensity can favorably impact on energy expenditure in a number of ways. First, exercise-associated energy expenditure is increased by decreasing exercise efficiency and increasing work rate. Second, resistance training that increases muscle mass, in turn increases resting energy expenditure. Third, aerobic exercise >70% VO2max, increases resting energy expenditure separate from any change in muscle mass. High-intensity exercise training has the added benefit of improving fitness, thus making low-intensity exercise less difficult and more easily tolerated. Although continuous intense exercise is difficult to maintain for extended periods of time, intense interval exercise can be easily endured and may be an important adjunct to lifestyle modifications for body weight control.

Energy expenditure and physical fitness in overweight vs non-overweight prepubertal girls

OBJECTIVE: To determine whether overweight children have lower physical activity energy expenditure (EE) and fitness levels than non-overweight children.STUDY DESIGN: Twenty-four healthy girls aged 7–10 y were divided into overweight (>95th percentile weight-for-height) and non-overweight (10–90th percentile) groups. Basal metabolic rate (BMR), sleeping metabolic rate (SMR), 24 h sedentary EE (SEE) and total EE (TEE) were measured by room respiration calorimetry and doubly labelled water. Physical activity EE and physical activity level (PAL) were calculated. Fitness (VO2peak) was measured by a treadmill exercise test.RESULTS: The overweight group had significantly higher body weight, percent fat, fat mass and fat-free mass (FFM) (P<0.001). The overweight girls had higher BMR, SMR, SEE and TEE (P<0.001), but not after adjustment for FFM. Physical activity EE and PAL were not significantly different between groups. After adjusting for FFM or weight, submaximal and peak VO2 were not significantly different between groups.CONCLUSIONS: We conclude that these overweight girls do not have lower physical activity EE or fitness levels than the non-overweight prepubertal girls, however, the rather high body fat of the non-overweight group may have precluded us from finding any differences between groups.

Effect of hydrolyzed guar fiber on fasting and postprandial satiety and satiety hormones: A double-blind, placebo-controlled trial during controlled weight loss

OBJECTIVE: To evaluate the effects of a completely soluble fiber on fasting and postprandial hormone levels, respiratory quotient (RQ) and subjective ratings of satiety during a controlled weight-loss program.DESIGN: In a five-week prospective, randomized, double-blind study, a 3.3 MJ (800 kcal)/d diet was provided during a two-week wash-in period. Then, during the intervention weeks, separated by a one-week wash-out period, a 3.3 MJ (800 kcal) formula containing either 20 g fiber or placebo daily, was given in a cross-over design and on days 1, 3 and 7 of the intervention weeks (weeks 3 and 5) measurements were taken after an overnight fast.SUBJECTS: 25 obese but otherwise healthy females (age: 46±6 y, body mass index (BMI): 35±6 kg/m2) were studied.MEASUREMENTS: Body weight; hunger/satiety ratings; glucose, insulin, cholecystokinin (CCK) and leptin concentrations; RQ during the intervention weeks.RESULTS: In the fasting state, the supplement had no effect on any of the measured parameters, including blood concentrations of glucose, insulin, CCK, and leptin, RQ and satiety ratings. In the 2 h postprandial period following the test meal, none of the measured parameters differed significantly from that following the non-fiber-supplemented meal, except for the CCK response. CCK demonstrated an overall higher concentration after the fiber-supplemented meal (P=0.007), even after adjustment for age, weight, height and treatment sequence. The postprandial peak in CCK also occurred earlier (at 15 min vs 30 min) after completion of the fiber-supplemented meal.CONCLUSIONS: The results indicated that a hydrolyzed guar gum fiber supplement produced a heightened postprandial CCK response, but did not alter other satiety hormones or increase satiety ratings, in either the fasting or the postprandial state.

Body fat: Its relationship to coronary heart disease, blood pressure, lipids and other risk factors measured in a large male population☆

Obesity is variably considered to be a major contributor to hypertension and hyperlipidemia, and its treatment is recommended in the management of coronary heart disease. Total body fat was measured by tritium dilution in a large male population and its relationship to age, blood pressure, serum lipids, uric acid and the diagnoses of coronary heart disease, hypertension and glucose intolerance was examined. In addition, three commonly used weight: height indices of obesity were correlated with each of these parameters. The correlation of body fat with blood pressure, serum cholesterol and triglycerides, although statistically significant, was of only small magnitude. Mean levels of body fat were not significantly different between patients with coronary disease and control subjects, whereas serum cholesterol and, to a lesser extent, systolic blood pressure were potent risk factors for the disease. It is concluded that obesity is only a minor determinant of blood pressure and lipid level, and that its contribution to coronary heart disease is small or nonexistent.

Effects of strength training on cardiovascular responses during a submaximal walk and a weight-loaded walking test in older females

PURPOSE The purpose of this study was to examine the effects of a total body strength training program on oxygen uptake (VO2), heart rate (HR), systolic blood pressure (SBP), and rate pressure product (RPP) during a submaximal walk and a weight-loaded walking test in healthy women 60-77 years old. METHODS The submaximal walk (2 mph and 3.5% grade) took place during stage 3 of a graded exercise test. The weight-loaded walking task consisted of treadmill walking at 2 mph while carrying a box weighing 40% of maximum isometric elbow flexion strength. The women strength trained three times per week for approximately 1 hour per session for 16 weeks. RESULTS Paired t tests determined that strength increased by 57% on six isotonic strength tests (one repetition maximum) and by 29% on two isometric strength tests. A repeated measures analysis of variance (ANOVA) was used to determine the pre- to post-differences between and within the two tests (alpha = 0.05). There was no change in VO2 but HR, SBP, and RPP decreased significantly during the submaximal walk and the weight-loaded walking test. However, average HR (135 to 120 bpm) and RPP (23.3 x 10(3) to 19.3 x 10(3)) decreased more during the weight-loaded walking test than during the submaximal walk (HR: 108 to 104 bpm; RPP 18.3 x 10(3) to 17.0 x 10(3)). CONCLUSIONS In conclusion, the reduced HR, SBP, and RPP indicates that strength training may reduce cardiovascular stress during daily tasks in healthy older women.