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Obesity: lifestyle activity versus structured aerobic exercise

While obesity rates have escalated, levels of physical activity have declined. For the overweight, a lifestyle approach to physical activity may be less formidable and more achievable than structured aerobic exercise. This randomised trial examines changes in weight, body composition and cardiovascular risk factors in obese women brought about by diet combined with either lifestyle activity or structured aerobic exercise.


A programme of diet plus lifestyle activity offers similar health benefits to a programme of diet plus structured aerobic activity for obese women.


RE Andersen et al. Effects of lifestyle activity vs structured aerobic exercise in obese women. Journal of the American Medical Association 1999 281: 335-340.


Participants were 40 obese women with an average age of 43 years, weight of 89.2 kg, height of 165 cm and body mass index of 32.9 kg/sq metre. Twenty-eight women were non-Hispanic white, ten were non-Hispanic black and two were Mexican-American. They were all a minimum of 15 kg over ideal weight and had not participated in a structured exercise programme for six months before the start of the study.

The women were interviewed to assess their weight, dieting histories, eating and exercise habits, and psychological status. Anyone with bulimia nervosa, binge eating disorder, significant depression or other psychiatric disturbances was excluded from the study. A medical evaluation (performed by their physicians) identified contra-indications to diet or exercise (e.g. a recent myocardial infarction or use of medications which would affect weight or energy expenditure).

The study was a 16-week randomised controlled trial which began in 1995 with a one year follow-up. The women agreed not to seek additional treatment during the one year follow-up period. All the women received a similar cognitive behavioural weight loss programme of 16 sessions in which they were instructed in behavioural methods of weight control (e.g. keeping daily food and physical activity records) and discussed ways of incorporating physical activity into their lifestyles. All the women were given the same diet: they were asked to consume a self-selected, low fat, low calorie diet of approximately 1,200 kcal/day. They were randomly assigned to either the low fat diet with moderate lifestyle activity or the low fat diet with structured aerobic exercise.

Lifestyle activity: the women were advised to increase their levels of moderate-intensity physical activity by 30 minutes a day on most days of the week; encouraged to walk instead of drive short distances, take stairs instead of lifts; and they wore monitors to provide information on levels of physical activity (used to calculate calorie expenditure).

Structured aerobic exercise: consisting of three step aerobic classes each week, building up to 45 minutes of stepping per class by the eighth week; total expenditure approximately 450 to 500 kcal per workout.

The following were measured at the start of the study, at 16 weeks and 68 weeks, by staff unaware of the women's assigned group:


Thirty-eight women completed the 16-week trial (nineteen in each group). Thirty-three completed the 68 week evaluation (16 from lifestyle group and 17 from aerobic group). Reported energy intake ranged from 1,195 to 1,265 kcal/d during the 16 weeks. The aerobic group attended an average of 88% of possible exercise classes. The lifestyle group had increased their daily physical activity by 234 kcal per day by week 16.

Weight loss

Weight losses did not differ significantly between the two groups. At week 16, average weight losses were 7.9 kg for the lifestyle group and 8.3 kg for the aerobic group. At the one year follow-up, the lifestyle group had regained an average of 0.08 kg and the aerobic group had regained an average of 1.6 kg.

Changes in fat and fat-free mass

At week 16, average body fat was reduced by 6.2 kg in the lifestyle group and 7.4 kg in the aerobic group. The percentage of body fat was reduced to 45.5% in the lifestyle group (from 48.5%) and 41.9% in the aerobic group (from 46.9%). Average reductions in fat-free mass were less in the aerobic group (0.5 kg) than the lifestyle group (1.4 kg).

Cardiovascular risk factors and mood

At week 16, significant reductions in serum triglyceride levels, total cholesterol levels and resting systolic blood pressure were found in all women, with no differences between groups. Significant improvements in maximum oxygen uptake were found with no differences between groups. See Table 1. The women had similar scores on the Beck Depression Inventory.

Table 1. Changes in cardiovascular risk factors at week 16 in women participating in diet with lifestyle activity and diet with aerobic exercise

Initial readings

Week 16

% change from initial readings

Triglycerides, mmol/L

Diet + lifestyle




Diet + aerobic




Cholesterol, mmol/L

Diet + lifestyle




Diet + aerobic




Resting SDP, mmHg

Diet + lifestyle




Diet + aerobic




Maximum oxygen uptake

Diet + lifestyle




Diet + aerobic





Weight maintenance

At the 12 month follow-up there were no differences between the groups' adherence to physical activity so they were treated as one group and divided into tertiles of self-reported levels of activity. The most active group lost weight in the year after the programme (an average of 1.98 kg), the middle tertile maintained their weight and the least active tertile regained some of their lost weight (an average of 4.88 kg increase).


This was a well designed and carried out trial, albeit small. The diet plus lifestyle programme was as effective as the diet plus aerobic training programme in improving weight, systolic blood pressure and serum lipid and lipoprotein levels. This is great news for people who dislike vigorous physical activity or believe that they lack the time to exercise.

The results also show the importance of an active lifestyle in helping to maintain weight loss. Energy intake will obviously also play a part. Details of the women's energy intake at the 12 month follow-up were not given, but it is likely that the most active group also restricted their energy intake the most and the least active group restricted it the least.