Behavior / Diet / Obesity

Sunday Funday, Tight Pants Monday: Weekly Weight Fluctuations

Why do my pants feel so tight?” This is the lament of the working adult getting dressed on a Monday morning, and one that I have struggled with as I button up, zip in, and head to work. With this uncomfortable ailment in mind, I set out to investigate just how bad the damage might be with respect to body weight, physical activity, and weekday-weekend differences.

First, let’s get to some basics. According to a review article on the topic, “Research literature indicates that the dietary quality is somewhat poorer on the weekends, characterised by higher fat intakes, higher alcohol intakes and consequently higher energy intakes. This increase in energy intake is not necessarily offset by an increase in activity, rather an increase in sedentary behaviours. Some research has observed an increase of more than 100cal per day over the weekend in American adults. Over the course of one year, this can result in a significant increase in body mass.”

 Indeed, this is not good! If you calculate the effect of an extra 100 calories/weekend day over the course of the year ((100 calories * 104 potential weekend days)/3500 calories per pound body weight), it turns out that this inequality can yield a weight gain of 3 pounds/year. While this may sound insignificant over the course of one year, it’s a little more substantial over 10 years.  I also came across an interesting study explaining the increased caloric intake on the weekends:  larger meal sizes on weekends are attributed to lengthier meals with a greater number of other people present. In other words, we eat more because it’s a social activity on the weekends. This is called “social facilitation” of meal size.

Taken from Obesity (Silver Spring). Aug 2008; 16(8): 1826–1830.Also revealing are these data assessing weight loss over a year in groups of adults randomized to a caloric restriction or exercise training intervention. At baseline, both groups gained weight on the weekends (and not on weekdays) because of higher caloric intake on Saturdays and reduced physical activity on Sundays. The accompanying graphs of energy intake (top) and physical activity expenditure (bottom) depict this trend. Over the course of the year, the caloric restriction groups demonstrated no weight loss on weekends, and the exercise training group actually gained weight on the weekends (because of higher dietary intake), leading to a slower-than-expected rate of weight loss in both intervention groups.

Interestingly, though, it appears that many people exhibit fluctuations in body weight across the week: this is normal. Body weight begins to increase on Saturday with the highest weight typically occurring on Sunday and Monday. By Tuesday, body weight begins to decrease again. What varies from individual to individual is how we compensate for those weekly weight fluctuations. Individuals who compensate for the weekend weight gain with a big loss in the latter part of the week lose or maintain weight. Those who don’t compensate effectively gain weight. This finding led authors of the above-referenced study to conclude that “weight variations between weekends and weekdays should be considered as normal instead of signs of weight gain. 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.”

So, there you have it! Pants tight on Monday does not a problem make…as long as they’re comfortable again by Friday.

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