Posted on Feb 14, 2014, 6 a.m.
How and why the seven-days-a-week human cycle affects weight.`
It is common for many people to lose a bit of weight on weekdays and gain a little weight on weekends. Brian Wansink, from Cornell University (New York, USA), and colleagues explored the role of the seven-days-a-week human cycle on weight. The researchers enfolled 80 adults, ages 25 to 62 years, who were categorized according to relative weight changes: weight losers (-3% weight loss), weight gainers (+1% weight gain), and weight maintainers (-3% to 1% weight change). The study participants were asked to weigh themselves after waking up before breakfast. The minimum follow-up time was 15 days and maximum 330 days. Weekly weight patterns were analyzed across the three groups: weight losers, weight gainers and weight maintainers. The results revealed a clear pattern in weekly weight fluctuation with higher weight after weekends (Sunday and Monday) and decreasing weight during the weekdays reaching the lowest point on Friday. Unexpectedly the researchers found a difference between weight losers and weight gainers in these fluctuation patterns. Weight losers had stronger compensation pattern (i.e. after weekend the decrease started immediately and continued downward until Friday) whereas weight gainers had more variability between days and no clear decrease during weekdays. Weight losers reached week’s maximum weight in 59% of cases on Sunday and Monday and week’s minimum weight in 60% of cases on Friday or Saturday. Among weight gainers no such a pattern was seen. Minimum and maximum weights did not systematically appear on certain days but they were evenly distributed all over the week. Observing that: “Weight variations between weekends and weekdays should be considered as normal instead of signs of weight gain,” the study authors suggest that: “Those who compensate the most are most likely to either lose or maintain weight over time. Long-term habits may make more of a difference than short-term splurges.”
Orsama A.-L. ; Mattila E.; Ermes M.; van Gils M.; Wansink B; Korhonen I. “Weight Rhythms: Weight Increases during Weekends and Decreases during Weekdays.” Obes Facts 2014;7:36-47.