Wayne C. Miller

How effective are traditional dietary and exercise interventions for weight loss

Health care professionals have used restrictive dieting and exercise intervention strategies in an effort to combat the rising prevalence of obesity in affluent countries. In spite of these efforts, the prevalence of obesity continues to rise. This apparent ineffectiveness of diet and exercise programming to reduce obesity has caused many health care providers, obesity researchers, and lay persons to challenge the further use of diet and exercise for the sole purpose of reducing body weight in the obese. The purposes of this paper were to examine the history and effectiveness of diet and exercise in obesity therapy and to determine the best future approach for health promotion in the obese population. A brief survey of the most popular dieting techniques used over the past 40 yr shows that most techniques cycle in and out of popularity and that many of these techniques may be hazardous to health. Data from the scientific community indicate that a 15-wk diet or diet plus exercise program produces a weight loss of about 11 kg with a 60-80% maintenance after 1 yr. Although long-term follow-up data are meager, the data that do exist suggest almost complete relapse after 3-5 yr. The paucity of data provided by the weight-loss industry has been inadequate or inconclusive. Those who challenge the use of diet and exercise solely for weight control purposes base their position on the absence of weight-loss effectiveness data and on the presence of harmful effects of restrictive dieting. Any intervention strategy for the obese should be one that would promote the development of a healthy lifestyle. The outcome parameters used to evaluate the success of such an intervention should be specific to chronic disease risk and symptomatologies and not limited to medically ambiguous variables like body weight or body composition.

Predicting max HR and the HR-VO2 relationship for exercise prescription in obesity.

This research derived regression equations for predicting maximal heart rate (MHR) and examined the relationship between relative oxygen consumption (VO2) and heart rate (HR) in obese (N = 86, body fat > 30%, hydrostatic weighing) compared with normal-weight (N = 51, body fat < or = 30%) adults. Simultaneous measurements of HR and VO2 were recorded at rest and every minute during a maximal graded exercise test. When MHR was regressed on age, two distinct equations for the obese and normalweights were generated. The relationship between %MHR and %max VO2 was similar between groups (r = 0.83, obese; r = 0.87 normalweights). Likewise, when %max VO2 was regressed on %max heart rate range similar equations were derived fro the obese (r = 0.81) and normalweights (r = 0.84). Correlation between Karvonens predicted HR at a submaximal VO2 and the true HR at that VO2 was 0.88, regardless of adiposity. These data indicate that when predicting MHR in normalweights the equation 220-Age can be used, but for obese individuals the equation 200-0.5 x Age is more accurate; each having 12 as a standard error of estimate. Once MHR is determined, either the straight percentage technique or Karvonens method would be appropriate for prescribing exercise intensity for both populations.

Early-Phase Adaptations of Traditional-Speed vs. Superslow Resistance Training on Strength and Aerobic Capacity in Sedentary Individuals

We performed a randomized exercise training study to assess the effects of traditional Nautilus-style (TR) or superslow (SS) strength training on muscular strength, body composition, aerobic capacity, and cardiovascular endurance. Subjects were 14 healthy, sedentary women, 19–45 years of age (mean ± SD age, 32.7 ± 8.9 years), randomized to either the SS or TR training protocols and trained 3 times per week for 10 weeks. Measurements were taken both before and after training, which included a maximal incremental exercise test on a cycle ergometer, body composition, and 1 repetition maximum (1RM) tests on 8 Nautilus machines. Both groups increased their strength significantly on all 8 exercises, whereas the TR group increased significantly more than the SS group on bench press (34% vs. 11%), torso arm (anterior lateral pull-down) (27% vs. 12%), leg press (33% vs. 7%), leg extension (56% vs. 24%), and leg curl (40% vs. 15%). Thus, the TR groups improvement in total exercise weight lifted was significantly greater than that of the SS group after testing (39% vs. 15%). Exercise duration on the cycle ergometer and work rate significantly improved for both groups, but there was no group-by-training interaction. No significant differences were found for body composition or additional aerobic variables measured. Both strength training protocols produced a significant improvement in strength during a 10-week training period, but the TR protocol produced better gains in the absence of changes in percentage of body fat, body mass index, lean body mass, and body weight. In addition, strength training alone did not improve Vo2max, yet short-term endurance increased.

Effects of clothing on accuracy and reliability of air displacement plethysmography.

PURPOSE The purpose of this investigation was to quantify the effects of different attire on the accuracy and reliability of estimating percent body fat (%fat) by using air displacement plethysmography (ADP). METHODS Fifteen adults were tested four times on four separate occasions. Each session consisted of estimating %fat with ADP wearing a swimsuit (ADP(SS)), a hospital gown (ADP(HG)), and in the nude (ADP(N)), plus assessment by hydrostatic weighing (HW). RESULTS An ANOVA revealed no significant differences within any of the four methods over the 4 days. Intraclass correlation coefficients revealed a strong relationship for repeated measures in ADP(SS) (r = 0.981), ADP(HG) (r = 0.993), ADP(N) (r = 0.989), and HW (r = 0.976). Mean data for each condition indicated a significant underestimation (P < 0.05) of %fat while wearing a hospital gown (13.8 +/- 7.7%) compared with ADP(SS) (22.0 +/- 7.8%), ADP(N) (23.5 +/- 7.5%), and HW (22.6 +/- 6.8%). CONCLUSION Reliability of ADP does not appear to be compromised by clothing; however, wearing a hospital gown significantly affects accuracy, reducing %fat estimations by approximately 9% compared with the recommended swimsuit. Measurement in the nude does not provide more reliable or accurate measures than wearing a swimsuit.

Diet composition, energy intake, and nutritional status in relation to obesity in men and women

There are dietary factors besides the total energy value of food that can affect adiposity by disrupting the balance between energy intake and expenditure. The purpose of this paper was to examine how perturbation of these dietary factors that control energy balance affects adiposity. There is a substantial amount of evidence suggesting that obesity is not associated with overeating, but with a high dietary fat-to-carbohydrate intake ratio. Physiological adaptations to energy-reduced dieting facilitate both weight regain and make it more difficult to lose weight during subsequent dieting attempts. Since obesity may be better characterized by diet composition than by energy intake, successful weight-loss programs should include diet compositional changes in their regimes.

Effective health promotion and clinical care for large people

Health and fitness professionals most often approach health care for large people in the context that health improvement can only be attained through weight loss. Unequivocal acceptance of the notion that thinness equals health and fitness presents an obstacle for large people who want to improve their health through lifestyle changes in eating and activity patterns and also weakens the working relationship between the health care professional and the large client. Since the health benefits of exercise and sound nutrition are significant for people of all sizes, the strategy for health care professionals should be to assist people of all sizes in eating healthier and becoming more active. Because large people face even more barriers to exercise than smaller people, we address the special needs of large people trying to become more physically active, outline an approach sensitive to their needs, and suggest how health and fitness professionals can improve their effectiveness with this population.

Role of the alkaline TG lipase in regulating intramuscular TG content.

Three TG lipases have been identified in muscle (i.e., acid, neutral, and alkaline), but as yet we do not know which enzyme is responsible for tissue TG hydrolysis. Over the past 8 yr, work in our laboratory has focused on intracellular lipoprotein lipase (LPL). The results show that this lipase is regulated by the classical cAMP cascade and that the activity of this enzyme is inversely related to endogenous TG concentration. Using these results as a foundation we plan to examine molecular mechanisms involved in the synthesis, compartmentalization, and transport of the alkaline TG lipase. Further, the evidence suggests that this enzyme may be regulated by protein phosphorylation mediated by cyclic AMP-dependent protein kinase. We plan to test this possibility.

Derivation of prediction equations for RV in overweight men and women.

PURPOSE The purpose of this research was to derive and compare regression equations for predicting residual volume (RV) in overweight and normal weight adults. METHODS RV was determined on land, in 311 men and women, following an overnight fast, using the nitrogen-dilution technique. Subjects were then weighed underwater at RV; 5-10 underwater weights were recorded; and the heaviest 3 measurements were averaged as the underwater weight. Percent body fat was calculated using the Siri equation. Group analyses were performed on overweight men (N = 59, body fat > 25%) and women (N = 126, body fat > 30%) compared with normal weight men (N = 68, body fat < or = 25%) and women (N = 58, body fat < or = 30%). A stepwise regression was performed for each group using the Systat Statistical Package (Evanston, IL). RESULTS When RV was regressed on sex, age (yr), body weight (kg), and height (cm), sex was not found to be a significant predictor variable for RV. Subsequent regressions revealed that prediction equations for the overweight (RV = 0.0277 AGE + 0.0048 WT + 0.0138 HT - 2.3967, F = 44.0, P < 0.0000, SEE = 0.403) were different from those generated for normal weight men and women (RV = 0.0275 AGE + 0.0189 HT - 2.6139, F = 58.6, P < 0.0000, SEE = 0.405). Similar equations were obtained when a cross validation was performed on a separate sample of normal weight (N = 31) and overweight (N = 46) men and women. CONCLUSION These data suggest that prediction equations for RV are separate and distinct for the overweight and normal weight populations.

Introduction: obesity: diet composition, energy expenditure, and treatment of the obese patient

The association of obesity with increased risks for developing hypertension, diabetes, cardiovascular disease, and cancer has made it a complex health problem. Exacerbating the problem is the realization that there are multiple factors, both physiological and psychological, that interact to induce obesity, as well as a myriad of components that may be useful in the curtailment of obesity. The aim of this symposium is to provide a wider understanding of the elements behind the development and reduction of obesity.

Activity patterns and perceptions about active transport to school

OBJECTIVES To document physical activity patterns and perceptions about active transport to school. METHODS Childrens activity was measured. Children and parents were surveyed about active transport to school. RESULTS Children were most active after (465 ± 20 cpm) and least active before (379 ± 18 cpm) and during school (351 ± 13 cpm). Weight was not related to activity. Boys were more confident than girls, whereas parents felt more confident than children did about active transport. CONCLUSIONS Active transport programs will likely have a greater impact on before-school activity than after school. Perceptions concerning active transport should be assessed, and parent/child discrepancies rectified prior to program implementation.