Maintaining a healthy body weight is one of the cornerstones of managing your health. Obesity is linked to a host of chronic, health problems, including cardiovascular disease, type 2 diabetes. Plus, it’s associated with as many as 13 types of cancer. Most people try to lose weight by modifying their diet alone – without exercise, but a new study points out another reason why exercise should be part of a comprehensive weight control plan. Adding exercise to your dieting and weight loss plans may help you preserve the very framework that holds you up – your bones.
Dieting and Bone Health: You Lose Bone Too!
When you go on a diet to lose weight, you hope you’ll lose only body fat, but the reality is that you shed muscle and bone. Most people don’t realize that dieting leads to bone loss as well. In fact, losing weight through diet alone can lead to substantial changes in the architecture of your bones. Researchers at the Hebrew Senior Life’s Institute of Aging at Boston University in conjunction with Beth Israel Deaconess Medical Center and the University of Calgary explored this connection. They used data from a large study called the Framingham Study that followed healthy men and women over a 40-year period.
Here’s what they found. Both short-term weight loss, over 4 to 6 years, and long-term weight loss over 40 years was linked to changes in bone architecture. These changes were apparent at a microscopic level and included a breakdown in the bones’ orderly structure that would lead to lower bone density and strength. In fact, their findings would elevate the risk of fracture by up to 3 times in those who lost more than 5% of their body weight long term.
When you consider how common osteoporosis, especially in women over the age of 50, this raises red flags about dieting, especially from the perspective of bone health. Plus, this isn’t the first study to show an association between losing weight and worsening bone health. Other research further shows that calorie restriction can impact bone integrity.
A study from Washington University in St. Louis looked at 46 overweight guys and gals who were trying to shed a few pounds. Half of the participants used dieting alone to lose weight. This group dropped their calorie intake by 20%, a seemingly healthy reduction in calories. The other half didn’t cut calories but burned 20% more calories through exercise.
The results? Both groups in the study lost weight, but the diet only group lost significantly more bone mass than the group that exercised. In fact, they lost bone in their back, hips, and thighs. As the researchers point out, exercise helps with weight loss, but it also stimulates the laydown of new bone tissue so that you don’t lose critical bone mass when you’re trying to slim down. Unfortunately, we don’t always consider our skeleton when we’re trying to lose stubborn body weight – but we should!
Can exercise prevent the loss of bone mass that goes along with dieting? Edward Puzas PhD., an orthopedics professor says “yes.” Exercise stimulates the laydown of new bone and aids in the delivery of key nutrients that support bone health. What kind of exercise is best? High-impact exercise or exercise that pulls on the bone enough to stimulate the formation of new bone.
High-Impact Exercise and Bone Health
High-impact exercise is movements where both feet leave the ground at the same time. It encompasses activities like running and jogging, but also plyometric moves that involve jumping. Squat jumps, long jumps, jumping lunges all apply enough impact to the bones to stimulate new bone formation. An old classic, jumping rope, works too and, of course, everyone’s favorite, burpees. In contrast, cycling will do little to boost your bone density since it’s low impact and the same goes for swimming as your body is supported during each activity.
The reality is not everyone can do high-impact exercise. If you have joint problems, it might be uncomfortable to jog or jump. That’s where strength training comes in. In fact, some studies suggest that strength training is the best strategy for preserving bone and muscle mass when restricting calories. However, you can’t pick up a pair of light weights and expect the sets you do to enhance your bone density. The resistance that you use needs to be at least 80% of your one rep max. You need this level of resistance to pull on the bone hard enough to lay down new bone tissue.
The minimal resistance you need to work your muscles against to stimulate your bones enough to grow is called the minimal essential strain. It’s equivalent to one-tenth of the force you’d have to apply to a bone to get it to break. When you lift at 80% of your one-rep max, you reach this threshold. So, more intense strength training is what builds bone – not circuit training. Also, you’ll get the most bone-building benefits from compound exercises, those that work more than one muscle group and involve the movement of more than one joint at the same time. It’s also important to do exercises that work your upper and lower body.
The Bottom Line
If you’re trying to lose weight by restricting calories, you need exercise. Exercise not only helps with weight maintenance and preservation of muscle tissue, but it also helps protect your bones. What could be more important than that? Also, don’t be too aggressive with calorie restriction. Focus on choosing nutrient-dense, whole foods that are naturally low in calories. Fruits and vegetables are always a good choice. Also, be patient! Getting down to your ideal body weight takes time and you want to do it in a healthy, sustainable manner. Focus on eating more mindfully as well. Be consistent and you’ll have a much better chance to reach your weight loss goals.
Science Daily. “Weight changes associated with reduced bone strength”
WebMD.com. “Weight Loss Can Mean Bone Loss”
Menopause. 2014 May; 21(5):501-8.
Curr Opin Endocrinol Diabetes Obes. 2014 Oct; 21(5): 358–362.
Menopause. 2014 May; 21(5):501-8.