El problema de la forma

Evidence regarding gender differences in compensatory responses is mixed and it is not clear if women are more susceptible to these changes; body composition changes suggest this may be the case but other factors may contribute. Further research is needed to determine if overweight and obese men and women differ in their response to exercise as at present no definitive evidence exists with this population group.

1.3.2.4 Rate and extent of compensatory changes in energy intake

There is evidence that compensatory changes are gradual and partial, although this evidence is obtained entirely from relatively small samples of lean

individuals. As these results provide some interesting information that could potentially apply to obese, or present a potential avenue for future research with overweight and obese, some discussion of these findings seems relevant.

Stubbs et al (2002b) provided evidence that compensation for ExEE in the short term was partial in lean women (33%). Further evidence suggested that these responses were also gradual in nature. Regression analyses of data from lean men and women completing a seven day exercise protocol revealed that small, gradual compensatory changes in both EE and EI occurred, acting to restore neutral energy balance in men and women. Changes in EI were equivalent to 0.2 MJ day^-1 and EE 0.35 MJ day^-1 (Stubbs et al, 2004). These findings were

corroborated by the findings of another study which reported that both male and female lean participants compensated for ExEE by approximately 30% during a 16 day exercise protocol (Whybrow et al, 2008), a figure strikingly similar to that previously reported in Stubbs et al (2002b; 2004b). There was also considerable individual variability in the extent of compensation in these participants, a finding which agrees with those of King et al, 2008. The small and gradual nature of compensatory changes observed here may also go some way to

explaining why so many studies do not detect these responses; studies of shorter and duration may not have the statistical power to detect changes which are gradual and therefore of rather small magnitude in the short term. Additionally, it is not clear from this evidence if full compensation would eventually occur in the long term. It should be noted that both of these studies are of short duration and small sample size, which may limit the strength of findings considerably.

There are mixed findings in the literature regarding the presence of exercise-induced compensatory EI responses, and a problem in this field is that such responses may occur and escape detection. It has been illustrated that there are three key factors which may contribute to this problem:

• Methods of assessing EI are lacking in accuracy, and many studies rely on self-reported measures which may give misleading values.

• Compensatory responses to exercise may be highly individual, and studies analysing only group mean values may fail to observe EI changes occurring in some participants.

• Compensatory changes may be partial and/or gradual, and therefore changes may be very small and thus even more difficult to detect.

90

There are clearly many factors to consider in this field, and there is a need for future studies to be more robust and try to minimise these problems. It may be that comparison of actual to expected body mass changes will provide a superior method of detecting compensatory responses since it is unlikely there will ever be an EI assessment method of sufficient accuracy to do so consistently.

91 Table 1.13 Evidence regarding the acute effects of exercise on energy intake in lean and overweight/obese men and women.

Authors Participants Mean BMI (kg/m²)

Intervention(s) Control

trial? Test meal Results

1 hour treadmill walking session conducted at

60% HRmax

Yes

Buffet lunch chosen from the normal selection of lunch foods

served in the university cafeteria.

Estimated ExEE: 628-837 kJ

Exercise had no effect on EI in either group, though overweight women ate significantly more than lean women at rest and post-exercise

(p=0.03).

Liquefied test meal served 15 minutes after intervention

period.

Intake of test meal was significantly lower (p<0.05) after high intensity cycling in the lean women but there were no differences in intake in

the obese participants (p>0.05).

Food intake (g):

test Yes Snack foods – cookies and crisps.

ExEE: not reported

No difference in EI between trials (p>0.05).

Those who reported increased negative mood after the step test consumed an average of 288 kJ more post-exercise than those who

reported no changes or a decrease in negative mood (p<0.05).

Visona &

Buffet lunch chosen from the normal selection of lunch foods served in the university cafeteria

and participants self-reported EI for the rest of the day.

ExEE: 916 kJ

No effect of exercise was seen on whole group EI at a post-exercise lunch test meal, or EI over the whole day (p>0.05).

92 Authors Participants Mean BMI

(kg/m²)

Intervention(s) Control

trial? Test meal Results

12 hour EI was significantly lower on day of control trial compared to exercise trial day in dieting women with high restraint only (p<0.01).

EI (kJ): exercise at 50%

VɺO2max

Yes Pasta based meal.

ExEE: Not reported

EI and REI were lower in exercise than control trial in both groups (p<0.001).

EI and REI during exercise trial were significantly lower in obese participants than lean participants (p<0.05).

No effect of exercise on appetite (p>0.05).

EI (kJ):

Yes Buffet lunch meal consisting of a selection of snack foods.

ExEE: 1471 ± 301 kJ (mean ± SD)

No difference in total EI (p=0.92), REI was significantly lower in exercise trial (p<0.001).

EI (MJ):

Control Exercise EI: 2.29 ± 1.2 2.31 ± 1.0 REI: 2.11 ± 1.2 0.83 ± 1.1

(Mean ± SD)

93 Table 1.14 Evidence regarding the chronic effects of exercise on energy intake in overweight and obese men and women.

Authors Participants Mean BMI (kg/m²)

mass (kg) Energy Intake results Attrition rate

Donnelly food intake was

observed, any

ExEE: 1674 kJ/session

No differences in EI between groups group (p>0.05). and dinner test meals served in laboratory at

ExEE: 10.5 MJ/week There was no significant change in EI between weeks 0 and 12 for the whole group

(p>0.05).

Non-compensators decreased EI by -544 kJ/day and C increased EI by 1121 kJ/day.

The difference in EI was significant between groups (p<0.05). and dinner test meals served in laboratory at

ExEE: 10.5 MJ/week

Non-responders increased EI by 686 kJ/day, and responders decreased EI by 527 kJ/day,

between baseline and week 12.

-

94 Table 1.15 Evidence regarding gender differences in the effect of medium and long term exercise interventions on energy intake responses in lean and

overweight men and women.

Authors Participants

Mean

mass (kg) Energy Intake results

Donnelly Women: 1846 ±385

EI was significantly greater in the exercise protocol, compared to control, for men only (p<0.05).

EI (kJ/day):

No significant differences in EI between trials (p>0.05).

Total daily EE (MJ/day Nex: 11.7 (ranges not reported)

Stubbs et

95 Authors Participants

Mean

mass (kg) Energy Intake results

±SEM) SEM) period. 1. Nex – no

There was a significant differences in EI between trials (p=0.035).

Total daily EE (MJ/day) Nex: 9.2 (ranges not reported)

Westerterp

Not reported 44 weeks

Aerobic exercise intervention with the aim of training to complete a

ExEE: Not reported

There was a tendency for men to increase EI and women to decrease, though this was not significant (p>0.05).

EI (MJ):

Baseline Week 40 Men: 11.8 ± 8.0 10.2 ± 7.1

Women: 9.1 ± 4.3 9.5 ± 6.3 (median ± range)

96