Is 'yo-yo' weight cycling bad for me?

Friday, December 07, 2018. Author Dr. Haran Sivapalan

Is 'yo-yo' weight cycling bad for me?

It was one of the most hyped boxing events of modern times: Tyson Fury vs Deontay Wilder. Part of the hype emanated from the former’s incredible return to fitness. Having defeated Vladmir Klitscho in 2015, former heavyweight champion Tyson Fury suffered a bout of mental health problems and his weight gradually skyrocketed to almost 400 lbs (181 kg). In the last year, however, Fury rapidly shed 130 lbs and got back into fighting form.

Another British boxer, Ricky Hatton, was also famed for his extreme fluctuations in bodyweight. When not training for a fight, Hatton often went on eating and drinking binges, allowing himself to swell to 30 – 40 lbs (13.6 – 18.1 kg) over his fight weight. Such off-season weight gain earned him the nickname “Ricky Fatton.”

But, trivial nicknames aside, are there more serious implications to ‘weight cycling’ – the name given to extreme yo-yoing in weight?

According to a recent study, published in The Journal of Clinical Endocrinology and Metabolism, the answer is: yes – greater body weight fluctuation is associated with a higher risk of death.

 

How was the study conducted?

Researchers followed 3,678 participants enrolled in the Korean Genome and Epidemiology Study over a period of 16 years. Participants’ weight and height were measured at regular intervals, while blood pressure, cholesterol levels, blood glucose levels and other health-related outcomes were collected every 2 years.

To grade fluctuations in body weight, the researchers looked at year-to-year changes in weight and calculated a statistic termed ‘average successive variability’ (ASV). Those with a higher ASV scores showed more extreme changes in weight.

 

What did the study find?

People with higher bodyweight variability (as indicated by higher ASV scores) tended to have a greater mortality risk, significantly higher blood pressure and higher fasting blood glucose levels. High fasting blood glucose typically signifies that the body’s tissues are poorly sensitive to the effects of insulin. This has consequences for tissue metabolism because insulin allows glucose to be taken up from the bloodstream and used by tissues (e.g. muscle, organs) for energy. Moreover, if levels of glucose in the blood are consistently elevated due to poor insulin sensitivity, this can lead to inflammation, cell damage and a higher risk of diabetes mellitus. Indeed, this study found that, for people with a healthy baseline BMI, higher bodyweight variability was associated with an increased risk of diabetes.

Interestingly, however, in subjects who were classified as overweight (BMI > 25 kg/m2), higher bodyweight variability appeared to have a small protective effect on diabetes mellitus. Nevertheless, this effect was outweighed by a higher risk of death from all causes.

 

Why does bodyweight fluctuate?

It’s thought that of those people who lose weight, 80% will end up regaining that weight or even putting more on. There are several complex reasons for this, some of which are behavioral. For example, someone may simply revert to unhealthy eating behaviors after a period of dieting, or they may fail to integrate exercise into their daily lifestyle. In the case of Tyson Fury, rapid weight gain was related to his depressive illness. While these behavioral factors are evidently extremely important, there are also various physiological reasons as to why someone’s bodyweight may fluctuate.

Just as a thermostat regulates the temperature of a room to a constant level, our bodyweight tends to hover naturally within a certain range. This is an example of what we call ‘homeostasis’ – the regulation of a constant internal environment. When we lose weight, levels of hormones that stimulate hunger (e.g. ghrelin) start to increase. Conversely, levels of hormones that signal satiety and tell us that we’re full (e.g. leptin, peptide YY and amylin) begin to decrease. This makes people more hungry and likely to overeat, thereby regaining weight.

Furthermore, adipocytes (cells that store fat) have a homeostatic tendency to stay the same size. As we lose body fat, adipocytes typically shrink in size. In compensation for this, however, adipocytes’ drive to store energy may increase. This can lead to a raised body fat percentage after initial weight loss. In line with this, when individuals first lose weight, they tend to lose more fat mass than lean muscle mass. When they regain weight afterwards, however, they tend to put on more fat compared to muscle, the develop poorer body composition.

So, if you’re planning to pile on the pounds this winter, with the hope of burning it all off in the summer, take note!

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