Influence of weekend lifestyle patterns on body weight

Abstract

Objective: To determine whether alterations in diet and/or activity patterns during weekends contribute to weight gain or hinder weight loss.

Methods and procedures: Randomized, controlled trial comparing 1 year of caloric restriction (CR) with 1 year of daily exercise (EX). Subjects included 48 healthy adults (30F, 18M) aged 50-60 years with BMI 23.5-29.9 kg/m(2). Body weight was measured on 7 consecutive mornings for a total of 165 weeks at baseline and 437 weeks during the 1-year interventions. Daily weight changes were calculated for weekends (Friday to Monday) and weekdays (Monday to Friday). Daily energy intake was estimated using food diaries; daily physical activity was measured using accelerometers. Both measures were validated against doubly labeled water (DLW).

Results: At baseline, participants consistently gained weight on weekend days (+0.06 +/- 0.03 kg/day, (mean +/- s.e.), P = 0.02), but not on weekdays (-0.02 +/- 0.02 kg/day, P = 0.18). This was attributable to higher dietary intake on Saturdays and lower physical activity on Sundays relative to weekdays (both P < 0.05). During the interventions, both CR and EX participants were in negative energy balance on weekdays (P < 0.005). On weekends, however, CR participants stopped losing weight, and EX participants gained weight (+0.08 +/- 0.03 kg/day, P < 0.0001) due to higher dietary intakes on weekends. This helps to explain the slower-than-expected rate of weight loss during the interventions.

Discussion: Alterations in lifestyle behaviors on weekends contribute to weight gain or cessation of weight loss on weekends. These results provide one explanation for the relatively slow rates of weight loss observed in many studies, and the difficulty with maintaining significant weight loss.

Figure 1

(a) Daily weight changes at baseline and (b) during the 1-year interventions. Symbols represent the mean for all participants (open circles, n = 48), caloric restriction (CR) group (filled circles, n = 18), exercise (EX) group (hexagons, n = 18) and healthy lifestyle (HL) control group (filled squares, n = 10). *P = 0.02 for daily weight change on weekends at baseline; *P < 0.005 for weight change on weekends or weekdays during the intervention year.

Figure 2

(a) Daily energy intake and (b) physical activity at baseline. Symbols represent mean values ± s.e.m. for all participants. *P < 0.05 vs. mean weekday value.

Figure 3

(a) Daily energy intake and (b) physical activity during the 1-year interventions. Symbols represent median values and interquartile ranges for the caloric restriction (CR) group (filled circles), exercise (EX) group (hexagons), and healthy lifestyle (HL) group (filled squares). *P < 0.05 vs. median weekday value.