VTT Technical Research Centre of Finland, in collaboration with Cornell University and Tampere University of Technology, has studied how people's weight fluctuates over the seven days of the week. A clear weekly rhythm was found, with weight highest after the weekend and decreasing trend during weekdays. A surprising finding arose when weekly fluctuation was studied among different weight management groups. Although there was a weekend weight gain across all groups, differences emerged in the weekday rhythm of weight gainers and weight losers.
For all groups – gainers, losers and maintainers – weight was highest on Sunday and Monday, after which weight began to decrease. The groups diverged as a result of different weight fluctuation pattern during weekdays. For the groups losing and maintaining weight, the decreasing trend in weight began on Tuesday and continued downward until Friday. The week's minimum weight was most frequently observed on Friday or Saturday. Weekday weight loss in the group of weight gainers lacked linearity, with minimum weight distributed across all days of the week.
The results indicate that weight losers succeed in compensating during the week for the slight weight increase gained during weekend. "Weight gain following a weekend can be thought of as normal weight variation. Some indulging during weekends and gaining a bit of weight isn't harmful from the weight management point of view as long as this is compensated by healthy food choices during the week. It is important to notice these rhythms and take steps to reverse the upward trend after weekend," says VTT research scientist Anna-Leena Orsama.
Weight loss and weight management is a question of lifelong change. More flexible food choices, unburdened by multiple constraints, are easier to assimilate and maintain over the longer term. Successful weight management emphasises a long-term energy balance that is unaffected by short-term weight gain.
The results are based on self-measurement data collected in four earlier VTT research projects in which subjects had been instructed to monitor and record their daily weight. Researchers analysed the weight development of 80 people aged 25–62 years on the basis of results for daily early morning weight. The minimum monitoring period was 15 days, and the maximum 330 days.
Advances in technology have brought various applications and devices available for self-monitoring of health and vital functions. The researchers aim to utilize the new data obtained without the steering influence of the authorities. These data contain valuable information on people's daily behaviour that could bring discovery of phenomena unobtainable using traditional research designs.
For more information:
Orsama, A., Mattila, E., Ermes, M., van Gils, M., Wansink, B., & Korhonen, I., (2013). Weight rhythms: Weight increases during weekends and decreases during weekdays. Obesity Facts, Forthcoming. http://www.karger.com/Article/FullText/356147
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