Does The Scale Tell Lies? Experts Weigh In On Why Our Weight Fluctuates

Person standing on weight scale

There is nothing more daunting, more baffling, and more frightening and downright intimidating…than the bathroom scale. Measuring our weight is an important aspect of staying healthy and fit, but why does the scale reveal one number and then hours later it’s completely different? Could you really have gained three pounds in one day? There are a number of reasons weight fluctuates during the day says Samantha Brody, a licensed naturopathic physician (primary care practice) and acupuncturist in Portland, OR. 1 She says it doesn't 'lie' but it does reflect more than our body's natural weight. What comes into play when we step on the scale? Dr. Brody says our weight will reflect:

  • Water intake
  • The actual weight of food we intake
  • Fluid retention (from salt intake, hormone fluctuation, or other things that impact fluid balance), clothing
  • Whether we've gone to the bathroom or not (if you have to urinate it can be up to a pound and if you don't have a bowel movement or there is backup that can be several pounds.)
  • Whether or not you've exercised

What's a normal scale swing?

Weight gain over the course of the day is completely normal and Dr. Brody usually recommends weighing first thing in the morning--not repeatedly throughout the day. “More than that I have people weigh weekly and pay attention to how their clothes are fitting in general. Sometimes healthy changes lead to weight gain (muscle) and when we are only looking at the scale it can give the wrong impression.”

Can what you have eaten recently cause a jump on the scale? Weight fluctuates normally, between two and four pounds daily, explains John La Puma 2 M.D. a Santa Barbara-based board-certified internist, nutritionist author of REFUEL. “Sodium is responsible for many weight swings, and processed food and food at restaurants have a lot of it,” he says. “But sodium increases weight excessively because it holds on to fluid, and extra fluid or too little fluid is the big reason. Drink a pint of water: you're a pound heavier. Eat a big meal, and you're two pounds (or more) heavier. Go to the toilet, and you'll lose a pound or even two.”

When to Weigh in

While it’s standard to weigh in once a day, it can be helpful to go a week—even two weeks without peeking at the number. "Concentrate on weighing yourself once a week, at the same time, and on the same scale, ideally upon awakening,” suggests  NYC personal trainer Maik Wiedenbach3, author of 101 FITNESS MYTHS. “Rather than weighing yourself every day, get used to weighing yourself only once, every two weeks. Keeping in mind that the scale does not represent loss of body fat accurately and only reports weight loss (or gain).”  An Ideal alternative to using a scale, he says is to have a friend or loved one take photographs of you when you would normally "weigh in" and be sure to take the photographs during the same time of day, in equal lighting and ideally with the same friend/loved one and device. More often than not, pictures will show more results than the evil and typically unpredictable common everyday bathroom scale!"

If weighing in only once a week is too long to wait, and you need a number on a daily basis to stay in check, Dr. La Puma says keep it consistent by   stepping on the scale the same time every day, same type of clothes and shoes (or none at all), and of course, the same scale. “I weight patients in my medical office the same way each time, in whatever way they always wear themselves, and have used the same "doctor's scale" for over 20 years. And for most people weighing every other day or every third day or even once a week is better: less obsessing about water fluctuation, and more focus on the long term goal.”

Additional sources not cited or linked to above:

  • 1 Interview: Samantha Brody, interviewed Sept 29, 2014
  • 2 John La Puma, interviewed  Sept 30, 2014
  • 3 Maik Wiedenbach, interviewed Sept 30, 2014
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