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Short versus long periods of exercise on weight loss and fitness

 

Treating obesity with dietary changes is successful in the short-term, but long-term weight loss is often not sustained. It is the combination of exercise with dietary change that maintains long-term weight loss, but exercise participation is often difficult to achieve in overweight individuals. Recent evidence suggests that multiple short bouts of exercise combined with dietary change may be an effective way to improve exercise adherence and weight loss in the short-term. However, the long-term implications of short bouts of exercise have not been examined. Furthermore, some studies have suggested that providing access to exercise equipment may improve exercise participation by making exercise more convenient. This randomised trial examines whether multiple short sessions of exercise, compared with one long session, improves weight loss in overweight women after 18 months. It also examines the effect of combining multiple short sessions of exercise with the use of home exercise equipment on weight loss.

Message

Among a small number of overweight women, multiple short periods of exercise (multiples of 10 minutes) are as beneficial as a single long period (40 minutes) in terms of weight loss and fitness (in combination with dietary change). Exercising for short periods of time with access to home exercise equipment improves exercise participation, with the following implications: improved long-term weight loss (as women who exercised more lost the most weight); and the need to address options to make exercise more convenient (e.g. incorporating several short brisk walks into everyday life).

Reference

JM Jakicic et al. Effects of intermittent exercise and use of home exercise equipment on adherence, weight loss, and fitness in overweight women. Journal of the American Medical Association 1999 282: 1554-1560.

Study

Participants were 148 overweight, sedentary women, aged 25 to 45 years. Their body weights were 20% to 75% higher than the ideal body weight (with an average body mass index of 32.8 kg/m2) and they exercised for less than 20 minutes a day on less than three days a week during the previous six months. Women were recruited through local newspaper advertisements in 1996 and were excluded if they had medical conditions that would limit their ability to participate in the study; were taking medication that would affect their body weight; had personal commitments that would limit their optimal participation; were pregnant within the previous three months, were currently pregnant or planning a pregnancy in the following 18 months.

Participants were randomly assigned to one of three groups. The amount of exercise was similar for all participants, but the groups differed in the way the exercise was prescribed (number and length of sessions and the availability of home exercise equipment). The exercise in all groups was home-based and participants were instructed to exercise at a pace similar to brisk walking.

Long-session group . Forty-nine participants were instructed to exercise on five days a week. Exercise time progressed from 20 minutes continuous exercise a day from week one to four; to 30 minutes a day from week five to eight; to 40 minutes a day until the end of the study.

Short-session group. Fifty-one participants were instructed to exercise on five days a week. Exercise time, divided into ten minute sessions, progressed from 20 minutes a day to 40 minutes a day by the ninth week.

Short-session/home exercise equipment group . Forty-eight participants were given the same instructions as those in the short-session group. They were also provided with home treadmills.

Eighteen-month behavioural weight-loss programme.

Participants attended regular group meetings taken by nutritionists, exercise physiologists and behavioural therapists on strategies for modifying eating and exercise behaviours. Participants were instructed to reduce both fat intake, to 20% of total energy, and daily energy intake to either 6,276 kJ/d (for those weighing 90 kg or more) or 5,021 kJ/d (for those weighing less than 90 kg). Participants recorded their dietary intake in a daily food diary which was reviewed on a weekly basis.

Assessments.

Throughout the trial, the following were assessed three to four times: weight, body composition, waist and hip measurements, cardiorespiratory fitness, heart rate and oxygen consumption (VO2). The relationship between heart rate and oxygen consumption (VO2) was assessed for the prediction of peak VO2 (VO2peak), i.e. a measure of aerobic capacity. Questionnaires assessed dietary intake and leisure-time physical activity. Height was also measured. The amount of weekly exercise performed was calculated from participants' records (which were verified by assigning participants to wear triaxial accelerometers for a randomly selected one week period).

Results

Of the 148 participants, 115 (78%) completed the 18-month trial: 37 in the long-session group; 36 in the short-session group and 42 in the short session/equipment group. There were no differences between the groups in participant characteristics at the start of the study or attendance at the meetings. The average percentage of meetings attended was 67.1% for the long-session group, 70.9% for the short-session group and 71.7%, for the short-session/equipment group.

Changes in body weight

Figure 1 shows weight changes for the three groups including all participants. For the 115 participants who completed the 18-month study the results follow a similar pattern:

Figure 1. Changes in weight by randomisation to exercise


Changes in body composition

  • There were no differences in body composition measures between the short-session and long-session groups (i.e. percentage of body fat, fat mass, lean body mass and bone mineral content).
  • Changes in percentage of body fat and fat mass were greater in the short-session/equipment group compared with the short-session group. Table 1 shows these changes (which also include body mass index).
  • There were no differences between the short-session/equipment and long-session groups.

Table 1. Changes in body composition.

 

Group

 

Long-session

Short-session

Short-session /equipment

Body mass index, kg/m2

0 month

32.9

33.2

32.2

18 months

30.8

31.9

29.5

Body fat, %

0 month

44.9

44.5

43.5

18 months

42.0

42.9

39.4

Fat mass, kg

0 month

40.2

40.5

38.4

18 months

35.7

37.8

32.4

Exercise participation

Figure 2 shows changes in exercise participation for the three groups.

Figure 2. Changes in exercise participation by randomisation to exercise


Leisure-time physical activity

All groups increased their leisure-time physical activity to a similar extent over the 18 months (long-session 2251.0 to 6378.1 kJ/wk; short-session 2680.7 to 5777.3 kJ/wk; short-session/equipment 2723.8 to 6199.9 kJ/wk).

Changes in energy intake

All groups decreased their total energy intake and percentage of energy consumed as fat, with no differences between the groups (shown in Table 2).

Table 2. Changes in total energy intake and percentage of energy consumed as fat

Group

Changes in energy intake (0 month to 18 months)

% fat of total energy intake (0 month to 18 months)

Long-session

7308.6 to 5874.8 kJ/d

37.9% to 33.6%

Short-session

8169.7 to 6716.6 kJ/d

35.3% to 32.3%

Short-session/equipment

8003.6 to 6178.5 kJ/d

35.1% to 32.9%

Changes in fitness

Cardiorespiratory fitness increased in all groups, with no differences between them (long session 9.9%; short-session 6.3%; and short-session/equipment group 17.1% predicted VO2peak).

Exercise and weight loss

Weight loss at 18 months was greater in participants exercising for more than 200 minutes per week (13.1 kg reduction) throughout the study compared with those exercising 150 to 200 minutes a week (8.5 kg reduction) or less than 150 minutes a week (3.5 kg reduction), shown in Figure 3.

Figure 3. Dose-response for exercise and weight loss


Comment

This study was well-designed and carried out with thought-provoking results, but they need to be considered in light of the small number of participants in each group.

Multiple short sessions of exercise were found to be no better than one long session in terms of long-term weight loss, exercise participation or cardiorespiratory fitness (although this may be because of the small number of participants). Nevertheless, another way of looking at these results is that multiple short periods of exercise are as beneficial as one long period and so provide an alternative effective way to exercise which is easier to incorporate into everyday life.

Although women lost a similar amount of weight in both the long-session and short-session/equipment groups, exercise participation in the long-term was greater in the latter group. This in turn will facilitate long-term weight loss as women who exercised more lost the most weight. Having immediate access to exercise equipment in the home may make exercising for short periods of time easier, more enjoyable and less intimidating than exercising in public.

The practical implications of this study are therefore:

  • in overweight women, multiple short periods of exercise are as beneficial as a single long period in terms of weight loss, exercise participation and fitness (in combination with dietary change);
  • multiple short periods of exercise can be incorporated into everyday life;
  • the more exercise taken, the more weight lost;
  • barriers to exercise participation need to be addressed (e.g. exercise needs to be convenient) and alternative options suggested (e.g. short brisk walks to the shops).