Research Review by Dr. Shawn Thistle©

Date:

2003

Study Title:

Physical activity and weight loss: does prescribing higher physical activity goals improve outcome?

Authors:

Jeffery RW, Wing RR, Sherwood NE, Tate DF

Publication Information:

American Journal of Clinical Nutrition 2003; 78: 684-689.

Summary:

There is ample evidence supporting the incorporation of exercise into weight loss plans (rather than just dietary modification alone). However, the optimal level of physical activity to facilitate long-term weight loss remains unknown.

This study, involving 202 subjects (men and women), evaluated the use of weight loss recommendations higher than those normally used in behavioral treatments.

General guidelines usually recommend aiming for an energy expenditure (EE) of 1000 kcal/week (that is, burning 1000 kcal through exercise). Many in the exercise sciences field feel this recommendation may be too low.

Subjects in this study were between the ages of 25-50, and were 14-32 Kg overweight according to actuarial norms. They were randomly divided into two groups: 1) a standard behavioral therapy group (SBT) - including an EE of goal of 1000 kcal/week OR 2) a high physical activity group (HPA) in which the goal was an EE of 2500 kcal/week. The subjects in the HPA group were also allowed to recruit 1-3 exercise partners into the study, personal counseling from an exercise coach and small monetary incentives.

The SBT group was involved in treatment sessions (involving < 20 people each) led by trained interventionists with expertise in both nutrition and exercise. Sessions were held weekly for 6 months, biweekly from 6-12 months, and monthly from 12-18 months for the SBT group. Intervention goals for this group were to reduce dietary intake by ~1000-1500 kcal/d (and consume < 20% calories as fat), and incrementally increase their EE from exercise to 1000 kcal/week.

The HPA group met on the same schedule as those in the SBT group and received identical training in dietary and behavioral skills. Their EE goal however, was 2500 kcal/week to be achieved by the end of the first 6 months of the study. This level of activity can be achieved by walking < 75 minutes/day.

The results of this study indicate that the HPA group achieved higher physical activity levels than the SBT group throughout the 18 month study period. Weight loss in both groups was evident, however, the HPA group experienced significantly more weight loss at the 12 and 18 month points in the study, indicating longer-term maintenance of weight loss that the SBT group.

Conclusions & Practical Application:

This study suggests that recommendations of higher levels of energy expenditure (~ 2500 kcal/week) through physical activity promote long-term weight loss in overweight adults better than the conventional recommendations of 1000 kcal/week EE.

Although the higher exercise levels did not result in higher rates of weight loss in the HPA group until 6 months, it should be noted that most in the HPA group did not reach the desired 2500 kcal/week EE until the 6 month point in the study.

Correlational analysis of the data also showed that the amount of energy expended on exercise was most strongly correlated with weight change, downplaying a potential argument that it may have been other aspects of the intervention that led to the weight loss.

For fitness professionals, this study adds to the evidence suggesting that increasing metabolic demands through increased exercise prescription leads to more sustained weight loss in adults. Aiming for an EE of 2500 kcal/week seems prudent, or at least an EE greater than the current standard recommendation of 1000 kcal/week.