Long-term efficacy of dietary treatment of obesity: a systematic review of studies published between 1931 and 1999

Long-Term (2???4 Year) Weight Reduction With Metformin Plus Carbohydrate-Modified Diet in Euglycemic, Hyperinsulinemic, Midlife Women (Syndrome W)

Long-term weight reduction remains the ultimate objective and challenge of obesity management. Few long-term dietary or pharmacointervention studies have been conducted and there is a critical need for long-range treatment strategies that are effective, safe, and acceptable. The authors conducted a retrospective cohort analysis of 21 euglycemic, hyperinsulinemic women with progressive, refractory, midlife weight gain (Syndrome W) who had previously lost weight (> or =10% reduction from baseline) with a comprehensive 1-year treatment program that included metformin and a hypocaloric, carbohydrate-modified (low-glycemic index) diet, as well as, other lifestyle modifications. The goal of the analysis was to determine long-term efficacy of the composite intervention using NHLBI criteria for weight stabilization, weight regain < or =3 kg (6.6 lb) in 2 years. Of a total of 26 consecutive women with Syndrome W who achieved goal weight during a 3-year period (1998-2001), 21 women (mean [standard error] age, 55.2 [2.4] years; mean body mass index, 34.2 [1.3] kg/m(2)) continued metformin and returned for annual follow-up visits. Weight maintenance was observed at the final (2-4 year) follow-up visit in 19/21 (90.5%) of women. Mean final follow-up weight (77.5 [2.8] kg) correlated highly with mean weight at 1-year protocol completion (77.2 [2.7] kg), (correlation coefficients r(xy) and sigma(xy) = 0.96, P = 0.000), demonstrating long-term weight reduction in the surveillance phase. Significant and robust decrements in fasting insulin (-28.4% [8.1%] to -43.4% [3.7%]) were observed at all follow-up visits (P < or = 0.002). This preliminary case series suggests that metformin may be an effective long-term adjunct to dietary and other interventions in the treatment of obesity in hyperinsulinemic patients. A randomized clinical trial of the dual regimen should be considered in nondiabetic women with midlife weight gain and hyperinsulinemia (Syndrome W) and, quite possibly, in additional euglycemic overweight and obese subjects with documented hyperinsulinemia and other portentous features of the Metabolic Syndrome.

Current management strategies for coexisting diabetes mellitus and obesity

Besides genetic predisposition, obesity is the most important risk factor for the development of diabetes mellitus. Weight reduction has been shown to markedly improve blood glucose control and vascular risk factors associated with insulin resistance in obese individuals with type 2 diabetes. Therapeutic strategies for the obese diabetic patient include: (i) promoting weight loss, through lifestyle modifications (low-calorie diet and exercise) and antiobesity drugs (orlistat, sibutramine, etc.); (ii) improving blood glucose control, through agents decreasing insulin resistance (metformin or thiazolidinediones, e.g. pioglitazone and rosiglitazone) or insulin needs (alpha-glucosidase inhibitors, e.g. acarbose) in preference to agents stimulating defective insulin secretion (sulphonylureas, meglitinide analogues); and (iii) treating common associated risk factors, such as arterial hypertension and dyslipidaemias, to improve cardiovascular prognosis. Whenever insulin is required by the obese diabetic patient after failure to respond to oral drugs, it should be preferably prescribed in combination with an oral agent, more particularly metformin or acarbose, or possibly a thiazolidinedione. When morbid obesity is present, both restoring a good glycaemic control and correcting associated risk factors can only be obtained through a marked and sustained weight loss. This objective justifies more aggressive weight reduction programmes, including very-low-calorie diets and bariatric surgery, but only within a multidisciplinary approach and long-term strategy.

A dietary and behavioural programme for the treatment of obesity. A 4-year clinical trial and a long-term posttreatment follow-up

OBJECTIVES

To evaluate weight loss maintenance after 4 years of nonpharmacological, nonsurgical obesity treatment, including a very low calorie diet (VLCD), diet and behavioural support. Furthermore, to assess weight development amongst completers and noncompleters beyond the active 4-year treatment period.

DESIGN

Clinical trial.

SETTING

Two Swedish county hospitals.

SUBJECTS

A total of 113 patients were randomized to a 2-year treatment programme with or without an initial VLCD period. The 87 patients who completed the 2-year programme were offered the chance to continue a support programme for another 2 years. A total of 55 patients completed the entire 4-year programme.

INTERVENTIONS

All the patients took part in a comprehensive support programme, including a hypocaloric diet and behavioural support, either as single treatment (non-VLCD group) or following the VLCD period (VLCD group).

RESULTS

Significant 4-year weight losses were found in both groups, 7.6 +/- 12.2 kg (VLCD group) and 6.3 +/- 8.5 kg (non-VLCD group), (P < 0.01, n.s. between groups). The completers (n = 55) had maintained a weight loss of 3.3 +/- 10.7 kg (P < 0.05) 8 years after randomization. After 6 years, the noncompleters (n = 58) had gained 3.2 +/- 9.7 kg compared with baseline (P < 0.05). The difference in weight change between completers and non-completers was highly significant (P < 0.01).

CONCLUSIONS

Highly significant weight losses can be maintained after a 4-year comprehensive treatment programme, including a hypocaloric diet and behavioural support. An initial VLCD period did not significantly affect the long-term weight loss. The posttreatment long-term weight loss was larger amongst completers than amongst patients who did not complete the treatment.

Leisure-time activity is an important determinant of long-term weight maintenance after weight loss in the Sibutramine Trial on Obesity Reduction and Maintenance (STORM trial)

BACKGROUND

The success rate of long-term maintenance of weight loss in obese patients is usually low. To improve the success rate, determinants of long-term weight maintenance must be identified.

OBJECTIVE

The objective of the study was to identify determinants of long-term success in weight maintenance in obese subjects who completed the Sibutramine Trial on Obesity Reduction and Maintenance (n = 261), a multicenter European study of weight loss and weight maintenance in obesity that combines sibutramine treatment with dietary restriction and advice on exercise and behavior.

DESIGN

We studied weight maintenance over 18 mo in subjects who had completed a 6-mo weight-loss phase. Factors included in the analysis were initial body weight, the percentage of initial body weight lost, dietary intake, various components of physical activity (measured with the Baecke questionnaire), the type of treatment (sibutramine or placebo), age, and sex.

RESULTS

Multiple regression analysis identified treatment group (sibutramine or placebo), the percentage of the initial body weight that was lost during the 6-mo weight-loss phase, and the leisure-time physical activity index as significant determinants of weight maintenance. Together, these 3 factors explained 20% of the variation in weight maintenance (P < 0.001). Dietary factors, age, and sex were not significant predictors of weight-maintenance success in this study.

CONCLUSIONS

Weight-maintenance success after weight loss is positively influenced by sibutramine treatment during weight maintenance, by a greater initial weight loss, and by a higher leisure-time physical activity index, which reflects higher levels of activities such as walking and cycling and lower levels of television viewing.

Treatment and prevention of obesity: what works, what doesn't work, and what might work

We provide a very broad conceptual overview of some of the issues involved in the treatment and prevention of obesity. Data suggest that clinicians have some ability to promote positive changes with obesity treatment. The environment, though important in influencing one's degree of adiposity, has largely transient effects that do not tend to carry over from one time to substantially later times. In contrast, the genetic influences on body mass index at any one time do tend to carry over to later times. This information influences the types of approaches that are and are not likely to be successful in terms of preventing obesity or reducing obesity on a population level. A second issue concerns the composition of weight lost. Conditional on fat loss, weight loss has been associated with an increased mortality rate (MR) whereas, conditional upon weight loss, fat loss has been associated with a decreased MR. This suggests that we should seek treatments that maximize the proportion of weight lost as fat. Third, the efficacy of current treatments is far below patients' expectations and desires. We need both to increase the efficacy of our treatments dramatically and help patients adjust their expectations so that they can take satisfaction in smaller weight losses. Perhaps, with continued efforts at enhancing treatments, we will see incremental advances in the treatment and prevention of obesity.

Effects of walking or resistance training on weight loss maintenance in obese, middle-aged men: a randomized trial

OBJECTIVE

To investigate whether walking or resistance training improves weight maintenance after weight loss when added to dietary counselling.

DESIGN

Two months' weight reduction with very-low-energy-diet (VLED) followed by randomization into three groups (control, walking, resistance training) for 6 months' weight maintenance (WM) program and 23 months' unsupervised follow-up. During VLED and WM all groups received similar dietary counselling.

SUBJECTS

The main inclusion criteria were BMI >30 kg/m(2), waist>100 cm and physical inactivity (exercise < or = once a week). Ninety healthy, obese (mean BMI 32.9 kg/m(2) and waist 112.5 cm), 35-50 y-old men started the study and 68 were measured at the end of the study.

MEASUREMENTS

Weight and body composition assessed by underwater weighing. Exercise diaries and dietary records to assess energy balance.

RESULTS

During VLED the mean body weight decreased from 106.0 (s.d. 9.9) kg to 91.7 (9.4) kg. Weight was regained mostly during follow-up and in the end of the study the mean weight in groups was 99.9-102.0 kg. Exercise training did not improve short or long-term weight maintenance when compared to the control group. However, resistance training attenuated the regain of body fat mass during WM (P=0.0l), but not during follow-up. In the combined groups the estimated total energy expenditure (EE) of reported physical activity was associated with less weight regain during WM. EE of 10.1 MJ/week was associated with maintaining weight after weight loss. EE of physical activity tended to decrease after WM in exercise groups due to poor long-term adherence to prescribed exercise. Energy intake seemed to increase during follow-up.

CONCLUSION

Exercise training of moderate dose did not seem to improve long-term weight maintenance because of poor adherence to prescribed exercise.

Advice on low-fat diets for obesity

BACKGROUND

Overweight and obesity are global health problems contributing to an ever increasing noncommunicable disease burden. Calorie restriction can achieve short-term weight loss but the weight loss has not been shown to be sustainable in the long-term. An alternative approach to calorie restriction is to lower the fat content of the diet. However, the long-term effects of fat-restricted diets on weight loss have not been established.

OBJECTIVES

To assess the effects of advice on low-fat diets as a means of achieving sustained weight loss, using all available randomised clinical trials. This review focused primarily on participants who were overweight or clinically obese and were dieting for the purpose of weight reduction. Since we were particularly interested in the ability of participants to sustain weight loss over a longer period of time, we focused on studies of 'free living' men and women who were given dietary advice rather than provision of food or money to purchase food.

SEARCH STRATEGY

We searched the Cochrane Library (issue 2, 2001), MEDLINE (up to February 20002), and EMBASE (up to February 20002). We also searched the Science Citation Index (up to January 2001) and bibliographies of studies identified. Date of latest search: February 2002.

SELECTION CRITERIA

Trials were included if they fulfilled the following criteria: 1) they were randomised controlled clinical trials of low-fat diets versus other weight-reducing diets, 2) the primary purpose of the study was weight loss, 3) participants were followed for at least six months, 4) the study participants were adults (18 years or older) who were overweight or obese (BMI >25 kg/m2) at baseline. Studies including pregnant women or patients with serious medical conditions were excluded. Two people independently applied the inclusion criteria to the studies identified. Disagreement was resolved by discussion or by intervention of a third party.

DATA COLLECTION AND ANALYSIS

Data were extracted by three independent reviewers and meta-analysis performed using a random effects model. Weighted mean differences of weight loss were calculated for treatment and control groups at 6, 12 and 18 months.

MAIN RESULTS

Four studies were included at the six month follow-up, five studies at the 12 month follow-up and three studies at the 18 month follow-up. There was no significant difference in weight loss between the two groups at six months (WMD 1.7 kg, 95% CI -1.4 to 4.8 kg). The weighted sum of weight loss in the low fat group was -5.08 kg (95% CI -5.9 to -4.3 kg) and in the control group was -6.5 kg, (95% CI -7.3 to -5.7 kg). There was no significant difference in weight loss between the two groups at 12 months (WMD 1.1 kg, 95% CI -1.6 to 3.8 kg). The weighted sum of weight loss in the low fat group was -2.3 kg (95% CI -3.2 to -1.4 kg) and in the control group was -3.4 kg (95% CI -4.2 to -2.6 kg). There was no significant difference in weight loss between the two groups at 18 months (WMD 3.7 kg, 95% CI - 1.8 to 9.2). The weighted sum of weight loss in the control group was -2.3 kg (95% CI -3.5 to -1.2 kg) and in the low fat group there was a weight gain of 0.1 kg (95% CI -0.8 to 1 kg). There was significant heterogeneity in the results for weight loss at six months and 12 months. Apart from one study which showed a slight but statistically significant difference in total cholesterol in the low fat group at one year follow-up, there were no significant differences between the dietary groups for other outcome measures such as serum lipids, blood pressure and fasting plasma glucose. Studies measuring other factors such as perceived wellness and quality of life reported conflicting results.

REVIEWER'S CONCLUSIONS

The review suggests that fat-restricted diets are no better than calorie restricted diets in achieving long term weight loss in overweight or obese people. Overall, participants lost slightly more weight on the control diets but this was not significantly different from the weight loss achieved through dietary fat restriction and was so small as to be clinically insignificant.

Very-low-calorie diets and sustained weight loss

OBJECTIVE

To review of the literature on the topic of very-low-calorie diets (VLCDs) and the long-term weight-maintenance success in the treatment of obesity.

RESEARCH METHODS AND PROCEDURES

A literature search of the following keywords: VLCD, long-term weight maintenance, and dietary treatment of obesity.

RESULTS

VLCDs and low-calorie diets with an average intake between 400 and 800 kcal do not differ in body weight loss. Nine randomized control trials, including VLCD treatment with long-term weight maintenance, show a large variation in the initial weight loss regain percentage, which ranged from -7% to 122% at the 1-year follow-up to 26% to 121% at the 5-year follow-up. There is evidence that a greater initial weight loss using VLCDs with an active follow-up weight-maintenance program, including behavior therapy, nutritional education and exercise, improves weight maintenance.

CONCLUSIONS

VLCD with active follow-up treatment seems to be one of the better treatment modalities related to long-term weight-maintenance success.