Influence of weekend lifestyle patterns on body weight.
OBJECTIVE
To determine whether alterations in diet and/or activity patterns during weekends contribute to weight gain or hinder weight loss.


METHODS
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.


CONCLUSIONS
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.
Racette
Susan B
SB
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA. racettes@wustl.edu
Weiss
Edward P
EP
Schechtman
Kenneth B
KB
Steger-May
Karen
K
Villareal
Dennis T
DT
Obert
Kathleen A
KA
Holloszy
John O
JO
D000203:Activities of Daily Living; D001835:Body Weight / Q000502:physiology*; D031204:Caloric Restriction; D015930:Diet Records; D002149:Energy Intake / Q000502:physiology; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D015430:Weight Gain / Q000502:physiology; D015431:Weight Loss / Q000502:physiology