Summary

In a 2-year study of overweight premenopausal women, strength training prevented percentage body fat increases, and lessened the proportion of intra-abdominal fat increase.

Introduction

American women between 25 and 45 usually gain about 1 to 2 pounds a year, chiefly as fat. Unfortunately, a lot of this is intra-abdominal fat, which is linked to obesity, morbidity (illness), and mortality. So any way to avoid this sort of fat accumulation would be welcome. Physical activity is clearly one place to start. University of Pennsylvania scientists have studied the effectiveness of strength training in premenopausal women, and published their findings in the American Journal of Clinical Nutrition. Here's a capsule of their findings.

What was done

The study was called the Strong, Healthy, and Empowered (SHE) study. Advertisements were used to recruit volunteers between 25 and 44 in the Minneapolis-St Paul area. They had to have a body mass index (BMI) between 25 and 35, be premenopausal, and take only limited physical activity (3 or fewer times a week with aerobic activity only). A medical history and exam was used to exclude women with health problems.

The women were randomly allocated to one of two groups - treatment or standard care - with the proviso that a balance was achieved between the groups with respect to age (roughly equal numbers aged 25 - 34 and aged 35 - 44) and percentage of body fat (using those above and those below the average).

Those in the treatment group were provided with a 2-year membership to local YWCA fitness centers. Initially they received 16 weeks of twice-weekly sessions supervised by a fitness professional. Full strength training was introduced after stretches, warm-up exercises, and abdominal and low-back strengthening had been taught. By the end of the first month the 1-hour sessions included 3 sets of 8-10 repetitions for each exercise, using isotonic variable resistance machines and free weights. During the second year the time of sessions was reduced to 45 minutes, and only 2 sets of 8-10 repetitions were done.

The 'standard care' group participants were mailed two brochures recommending 30 minutes' moderate exercise on most days of the week. Both groups of participants were asked not to make dietary changes that might influence their weight.

Assessments were made at baseline, and after one and two years. Body composition was measured by dual-energy X-ray absorptiometry (DXA), and abdominal fat areas (total, subcutaneous, and intra-abdominal) were obtained by CT scan. Muscle strength changes in the maximum bench press and leg press weights were measured, and treadmill tests were done.

What was found

Of the 164 women who entered the study, 70 of 82 completed the 2-year treatment period, and 63 of 82 completed the standard care period. Their average age was 36; 26% were black, 69% had a college degree, and 53% were married.

In the treatment group, adherence to the regime was highest during the early supervised period; it averaged 71% over the full two-years. The strength training was effective in raising bench and leg press weight lifts. Members of the treatment group lifted, on average, 9.5% greater maximum weights after two years than they could at baseline.

Lean body mass and body mass index did not increase significantly in either the treatment or control groups. However, there was a significant greater decrease in percentage of body fat, compared with that in the control group - minus 3.68% vs. minus 0.14%.

More dramatic was the difference in the proportion of intra-abdominal fat. In the treatment group there was an average increase of 7.1%, but in the control group it increased 21.4%.

Conclusions

This study showed that strength training in overweight premenopausal women was able to prevent percentage body fat increases and could attenuate intra-abdominal fat increases. Thus strength training is an important addition to the various ways women (and men) can avoid one of the more serious risk factors for cardiovascular disease - increased intra-abdominal fat. Recent emphasis on the use of waist circumference as a metabolic syndrome factor makes it clear that the distribution of excess fat is relevant.

Realizing a successful resistance training program is not as easy as implementing aerobic workout programs. The apparent benefits are not easily measured, and enthusiasm for the program can drop. Gym memberships are expensive, and a strength program done at home usually requires weights and/or expensive apparatus to achieve the best result. However, if it can be arranged, and combined with an aerobic routine, the outcome will be well worth while.