In medical school I learned that changes in body weight can be an important indicator of health risks. In infants we track weight on growth curves to detect early signs of health problems. In older individuals, unintentional weight loss is generally a sign of severe underlying illness.
So, yes, measuring and recording body weight should be part of every routine medical visit.
But what do these numbers on the scale really mean for someone who is otherwise healthy?
Interestingly, not much. According to the latest research, weight alone (or body mass index, a measure of weight in proportion to height) is far less a marker of poor health than previously thought.
Indeed, we know that other health indicators including having elevated blood sugar, blood pressure or cholesterol levels are far more powerful predictors of health risk than simply looking at numbers on the scale.
This is because body weight, even if were an accurate measure of body fat (it is not), does not really tell us much about whether or not that fat poses a health risk.
Thus, we now know that the actual location of excess fat is far more important for your health than the absolute amount. Having fat around your midsection (or even worse, inside your tummy) can dramatically increase your risk for diabetes and heart disease, whereas the same amount of fat around your hips and thighs may well protect you from these very problems.
In addition the cellular structure of your fat tissue can determine its health impact. Thus, body fat distributed across many small fat cells appears to be far less of a health problem that the same amount of body fat distributed across a fewer number of large fat cells.
Also, whether or not there are signs of inflammation in your fat tissue appears to matter in terms of how your fat affects your health.
Unfortunately, none of these factors can be measured by simply stepping on a scale. It does take a visit to your doctor's office to determine whether or not your body fat is affecting your health.
On a positive note, we know that good health is possible across a wide range of body weights and depends far more on whether or not you exercise and eat a healthy diet than on what you weigh. Indeed, it is far better to be fit and fat and than it is to be unfit and skinny.
Research also suggests that people who are unhappy with their weight tend to have more health problems than people who are not.
Clinically, the question is never about how much body fat my patients have – it is only about whether or not their body fat is affecting their health. This is why, a few years ago, we invented the Edmonton Obesity Staging System, which classifies people with high body-mass index not according to how "big" they are but rather according to how "sick" they are.
This does not mean we should throw out our scales. Changes in body weight can be indicators of health problems and regular weighing can help those who need to better manage their weight because of specific health problems. But for most of us, simply stepping on a scale will tell us far less about our actual health than many of us believe.
Arya M. Sharma is Professor and Chair in Obesity Research and Management at the University of Alberta. In 2005, he spearheaded the launch of the Canadian Obesity Network. He is also Past-President of the Canadian Association of Bariatric Physicians and Surgeons. Dr. Sharma maintains a widely-read blog on obesity prevention and management. You can follow him on Twitter @DrSharma