We all know reducing body fat is a good thing, at least to a point. It’s good for athletes because it generally improves performance, and it’s good for the rest of us because it makes us healthier and helps us live longer. The problem is, there’s an unseen deleterious consequence of weight loss: a reduction in bone health and bone strength. In a recent study in the Journal of Strength and Conditioning Research, this topic was investigated during a year-long trial.
The study looked at obese kids specifically, although the researchers also discussed much of the prevailing science covering people of all ages. On the surface it looks like the study merely shows that exercise is good for overweight people, but this is not necessarily the case.
Oddly enough, weight loss may not be good for everything. While it’s true that visceral fat – the kind that’s deep inside your body in and around your organs – may secrete inflammatory chemicals that damage your bones, generally fat is considered to be good for bone health. Subcutaneous fat, which is the fat stored under your skin, has been repeatedly shown to correlate to stronger and healthier bones. On the surface this may seem bizarre, but the fact is that resisting gravity all day keeps your bones strong. If you have more weight, your bones need to work harder to keep you moving, and they respond by getting stronger just like your muscles do. This is why astronauts have to exercise in space. The lack of gravity weakens their bones.
When we lose weight, not only do our bones have to work less to overcome gravity, but it’s also possible that a chronic catabolic state – the state of the body in which we break down tissues like fat and bone – may make the issues worse. When we finish a period of weight loss, we may come on the other end with reduced bone health and less bodyweight to help rebuild bone strength. This problem can be compounded in yo-yo weight loss situations.
In this study, the researchers followed the results of two groups of adolescents for a year. Each group received nutritional, psychological, and physical interventions, meaning they were coached in every facet of weight loss. One group did only aerobic exercise, and the other did aerobic exercise along with weight training.
Both groups lost weight, and both had better insulin levels and reduced fat. That’s the unsurprising news. However, only the resistance training group showed improvements in lean tissue, including bone mass and content. The resistance group successfully kept the harmful effects of weight loss at bay, and actually improved bone health, whereas the aerobic-only group maintained bone health. Interestingly, the aerobic-only group ran, which is often shown to improve bone health. Perhaps this difference was due to the fact that they ran on a treadmill.
According to the results of the study, this problem has a clear solution. All you have to do is follow the common advice. If you’re trying to lose weight, don’t just stick with cardio training and diet changes. Make sure you’re also getting in your weight training. You’ll look better and be stronger and healthier if you do.
1. Raquel Campos, et. al., “Aerobic Plus Resistance Training Improves Bone Metabolism and Inflammation in Obese Adolescents,” Journal of Strength and Conditioning Research, DOI: 10.1519/JSC.0b013e3182a996df
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