The Role of Physical Activity in Producing and Maintaining Weight Loss: The Role of Physical Activity in Maintaining Weight Loss

The Role of Physical Activity in Maintaining Weight Loss

Twelve RCTs were identified that had investigated weight regain after weight reduction.^[44-55] For inclusion in this review, the RCTs had to compare an exercise-based weight-maintenance program with a control, and report a follow-up period of at least 1 year after weight reduction. The design of these studies varied considerably; they are presented in two distinct groups in Table 3 and Table 4. The average BMI ranged from 30 to 38 kg/m², though the BMI was not explicitly reported in several studies.^[47-51] The exercise interventions ranged from 60 min to 300 min per week.

Eight RCTs randomized individuals to diet versus diet plus exercise intervention (Table 3) with follow-up of greater than one year after completion of the intervention.^{[47,48,50-55]} The duration of the weight-loss intervention was less than 1 year in all studies. In more than half of these studies^{[47,48,50,52,54]} the initial weight reduction intervention was 20 weeks or less in length. Little or no supervised intervention was prescribed in the maintenance period.

Only a few studies evaluated the impact of a physical activity intervention during the weight-loss maintenance phase. We identified four RCTs that compared physical activity interventions with a sedentary control group after initial weight reduction (Table 4).^[44-46,49] These studies began with a 12–26-week weight-loss intervention, after which individuals were randomly assigned either an exercise intervention or control intervention for a 26–40-week weight-maintenance phase, with a subsequent minimally supervised follow-up period. In most of these studies, the individuals in both arms were given advice to continue some degree of dietary modification.

Overall, only four studies showed significantly less weight regain at follow-up in the group assigned to exercise either during the weight reduction intervention^[47,50,54] or the weight maintenance intervention;^[45] however, in the majority of studies^{[45,47,49-55]} exercise produced a weight difference that favored the exercise group of, on average, -4.5 kg at longest follow-up.

Several meta-analyses and systematic reviews have addressed the role of exercise in weight-loss maintenance. Miller et al.^[21] reviewed 152 studies (not limited to RCTs) that had evaluated diet, exercise, or diet plus exercise and reported at least 1 year of follow-up data. At 1-year post program, the mean amount of weight loss maintained (6.6 kg, 6.1 kg and 8.6 kg in the diet, exercise or diet plus exercise group, respectively) was greatest in the diet plus exercise group, though this result was not significant.

Curioni and Lourenco^[56] reviewed RCTs "published through March 2003" comparing diet plus exercise interventions with diet alone, all with follow-up greater than 1 year after initial intervention. In the six studies they identified, programs that included both diet and exercise produced a 20% greater weight loss than diet alone by the end of the intervention period and at 1-year follow-up. Fogelholm and Kukkonen-Harjula^[57] reviewed all research reports published between 1980 and early 2000 that had data on physical activity and weight gain or regain with follow-up of more than 1 year. Prospective observational studies (16), nonrandomized studies (19), and RCTs (11) were included. The results from observational studies, but not clinical trials, suggested that exercise leads to successful weight-loss maintenance.

A central issue in the effectiveness of a physical activity program is adherence; poor adherence to a given exercise protocol might be one of the main reasons why RCTs so often fail to find an association between physical activity and weight maintenance.^[22] In many of the RCTs we reviewed substantial proportions of patients did not complete exercise interventions. The 1986 study by Perri et al.^[48] reported that 42% of individuals assigned the exercise intervention reported no exercise at 18 months of follow-up. The remaining 58% of individuals reported an average of only 46 min per week.

Van Dale et al.^[52] reported that 72% of individuals discontinued the exercise training after completing the initial 12-14-week treatment phase. Wadden et al.^[53] reported that participants in his study attended only 57% of exercise sessions during weeks 25-40 of the exercise intervention. The 1998 study by Wing et al.^[55] reported that attendance at group exercise sessions during the initial 6 months was 56- 70%; however, attendance dropped to 16-37% in months 6-12. A poor relationship between exercise interventions and prevention of weight regain in RCTs is, therefore, not surprising.

Observational and cross-sectional studies provide more consistent results concerning the role of physical activity in weight-loss maintenance.^[58-60] For example, data from the National Weight Control Registry (NWCR) support the idea that high levels of physical activity are critical to weight-loss success. The NWCR is a registry of over 6,000 individuals who have maintained a minimum 13.6 kg weight loss for at least 1 year; the average weight loss is 30.4 kg maintained for a mean duration of 5.5 years. NWCR members report expending an average of 2,682 kcal per week by means of physical activity, and nearly 90% report regular exercise.^[60]

Using the gold-standard doubly labeled water method to obtain activity levels, Schoeller et al.^[61] and Weinsier et al.^[62] found that 77-80 min per day of moderate intensity activity added to a sedentary lifestyle was needed to prevent weight regain in the year after weight loss.

Long-term follow-up data from non randomized, prospective, interventional studies also suggest a critical role for physical activity in weight-loss maintenance. Fogelholm and Kukkonen-Harjula^[57] reviewed 13 non randomized, weight-reduction studies that had a prospective follow-up of more than 1 year and found that most results were consistent: 12 of 13 studies reported that a large amount of physical activity at follow-up was associated with less weight regain after weight reduction.

Several of the RCTs we reviewed also show a strong retrospective relationship between amount of exercise performed at follow-up and maintenance of weight loss. Wadden et al.^[53] found that the greater the number of minutes participants walked in the 4 months before follow-up, the less weight they regained (co efficient of correlation -0.44, P <0.05). Fogelholm et al.^[45] reported that daily physical activity, as indicated by a higher number of daily steps, was a positive and independent predictor of weight maintenance after a very-low-calorie diet. Wing et al.^[54] compared individuals reporting low (using 168-616 kcal per week), medium (700-1,200 kcal per week) and high (1,372-4,116 kcal per week) levels of exercise at 1 year follow-up and found weight losses of -2.3, -5.9 and -9.1 kg respectively (P <0.01).

Other prospective studies have also found that when data were examined on the basis of how much exercise was actually performed, greater levels of exercise were associated with improved weight loss maintenance at follow-up.^[63,64] Jakicic et al.^[64] studied 201 overweight or obese sedentary women enrolled in a 12-month behavioral weight-loss intervention. Enrolled women were randomly assigned one of four exercise regimens involving different estimated energy expenditures and exercise intensities. No significant effect of either exercise intensity or duration on the changes in body weight between groups was reported; however, when data were analyzed in a post hoc analysis on the basis of how much exercise was actually performed, weight loss at 12 months was significantly greater in the group with >200 min per week of exercise (11.6 kg) compared with the group with less than 150 min per week of exercise (3.8 kg). In addition, women averaging approximately 280 min of exercise per week showed no weight regain from 6 months to 18 months of treatment.

A prospective study published in 2003 by Jeffery et al.^[65] provides direct evidence for a relationship between the amount of exercise performed and long-term weight-loss maintenance. Overweight men and women in a behavioral therapy program were randomized to standard behavioral therapy (energy expenditure goal of 1,000 kcal per week) or a high level of physical activity group (energy expenditure goal 2,500 kcal per week). At 18 months, the standard behavioral therapy group averaged 1,629 kcal per week whereas the high physical activity group averaged 2,317 kcal per week. Energy intake (self-reported) was the same in both groups. Mean weight loss at 6 months was no different between the groups, but weight loss was significantly greater in the high physical activity group than in the standard behavioral therapy group at 12 months (-8.5 ± 7.9 kg versus -6.1 ± 8.8 kg [mean ± SD]) and at 18 months (-6.7 ± 8.1 kg versus -4.1 ± 8.3 kg).

Despite the mixed results of the RCTs presented in Table 3 and Table 4, cross-sectional and prospective correlation studies strongly support the important role of physical activity in weight-loss maintenance. Retrospective analyses demonstrate that when high levels of physical activity are actually performed a very strong relationship between activity and weight-loss maintenance is consistently observed.