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To Weigh or Not to Weigh?

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When it comes to health advice, the internet tends to contradict itself. The benefits of food get flipped around, and longstanding fitness tips can suddenly be deemed ineffective. Self-weighing is another one. Don’t jump on the scale – it’s counterproductive and will drive you crazy. Or, step on it – it’s motivating and keeps you in check. So, which is it?

Research in scientific journals tips the scale in favor of frequent self-weighing. The tactic can be an effective, self-monitoring behavior for people looking to lose or keep off weight, more and more studies show. 

Take this recent one in the Journal of Behavioral Medicine from researchers at Penn and Drexel University, who followed 294 college-aged women (18 and 19 years old) from universities in Philadelphia for two years. That’s during a time when 70 percent of students (both women and men) tend to gain weight – the dreaded “Freshman 15.” 

The women who reported at least one period of daily self-weighing saw a drop in both body mass index (BMI) and body fat percentage, while the BMI of women who never engaged in daily self-weighing over that time remained steady.

Keep in mind these are women of all shapes and sizes who weren’t on a weight loss program. Most studies of daily self-weighing have focused on overweight or obese people working to slim down.

BMI – a formula that divides weight by height equaling out to a number of units, like 18 or 20 – decreased by approximately 0.5 units by the first year in women who self-weighed. There was a small increase in the second year, but it wasn’t statistically significant. While body fat increased somewhat in the first six months for everyone, the subsequent decrease was greater for the daily self-weighers, resulting in declines of around two percent.   

Those may seem like small increments, but they represent a statistically significant shift compared to those who never engaged in daily self-weighing, and suggest an impact. To be fair, though, based on the data from this study (which was not a randomized controlled trial), researchers can’t infer that it’s the direct cause of the more favorable trajectories. But, it does suggest that the behavior could be useful, said Diane Rosenbaum, PhD, a psychologist at Penn’s Aaron T. Beck Psychopathology Research Center, and author on the study. 

“Daily self-weighing only adds a few extra minutes to someone’s morning routine, but it has the potential to help individuals stay on track with health goals, which is another reason it could offer a lot of utility for folks looking to watch their weight,” she said, adding: “It gives you more opportunities to see the impact of your behaviors on your weight, and helps you to identify when you may need to make adjustments sooner rather than later.”

Other studies have turned out similar findings.

2016 study in Obesity, Science and Practice from researchers at the Virginia Commonwealth University School of Medicine found greater weight loss among younger adults who weighed themselves more times a week. Another paper, published in the Journal of Obesity in 2015, found that frequent self-weighing among adults looking to shed pounds was an effective way to lose a modest amount of weight and keep it off after two years, especially for men. That came from David Levitsky, PhD, a nutritionist at Cornell University, who has authored several papers on self-weighing, with much the same result.  

“Stepping on the scale should be like brushing your teeth,” he told USA Today last year.

Studies questioning the link between weight loss and regular self-weighing do exist, but most of the anti-scale sentiment comes from trainers and self-identified weight professionals vetoing the practice in online forums and communities. 

One blogger and founder of a fitness program geared towards plus-size women swore against it in a Self magazine piece in July: “…[T]he scale is often the culprit in our lack of follow-through. Instead of looking at the numbers on a scale, which barely tell you anything, measure your success by how good and strong you feel.”

Another trainer opined on the blog Thrillist this past December: “After a lifetime of dieting, losing weight, and then gaining it back, I finally got to a comfortable weight. I've maintained that weight for over a decade, in part because I finally stopped using this machine: the bathroom scale.”

The Self blogger did bring up a valid point about the scale in her piece: it can mislead those packing on muscle. Although she watched digits go up instead of down, it was because she was replacing fat with muscle. Indeed, a good marker of progress is body fat percentage, not just BMI or pounds, experts have said, which is why the Penn and Drexel researchers included it in their new study.

“One of things that people critique about using BMI is that it can sometimes be confusing to interpret in people who are high in muscle mass,” Rosenbaum said. “If we look at body fat specifically, we can say a lot more concretely that the changes we are seeing are related to gaining body fat, as opposed to any other type of weight gain or loss. And that’s useful because we know that excess body fat is one of the things that can be a predictor of future health problems.”

While some people may advise against the scale, professionals in the structured programs, those used in research and commercial settings, are likely to recommend regular self-weighing, said Jena Shaw Tronieri, PhD, director of Clinical Services at Penn’s Center for Weight and Eating Disorders.

She encourages her patients to weigh themselves regularly as part of their overall weight loss plan because doing so provides the feedback they need to gauge their progress – or lack thereof.  

“My training is in health and clinical psychology, so my clinical recommendations come from a research-based perspective,” she said. “Most research suggests a relationship between regular self-weighing and better weight loss or weight loss maintenance, though further studies are needed to determine that one actually causes the other” – rather than being merely associated.

Getting the message across can be tough, though, especially with so many competing ideas floating around the internet.

“Generally, dissemination of what works and what doesn’t is lacking in health behavior research,” Tronieri said. “That makes it hard for the public to determine which behaviors are most likely to be helpful because there are so many stories out there about what’s good for you and what’s not.”

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