Exercise for Bones

By Dietitian, Juliette Kellow BSc RD

A new study has confirmed how important it is to include exercise as part of a weight loss programme – not just for the effect it has on shifting those pounds, but also because it helps keep bone health.

The research, published in the Archives of Internal Medicine, set out to identify the effect that losing weight – either by restricting calories or by exercising – had on bone mineral density (a measurement that helps to determine the strength of bones).

The study included 48 adults in their 50’s who had a BMI between 23.5 and 29.9. The participants were assigned to one of three groups for a year: one group restricted calories by 20 percent; one group exercised predominantly by walking or jogging to create a 20 percent calorie deficit; and one group followed a healthy lifestyle. After one year, the calorie-restricted group had lost, on average, 10.7 percent of their body weight, while the exercise group lost 8.4 percent.

However, as well as losing weight, the participants who followed the low-calorie diet also had a reduction in their bone mineral density in the hip and spine. In contrast, bone mineral density wasn’t affected by weight loss in the participants who exercised.

The researchers conclude that weight loss caused by reducing calories is linked to a reduction in bone mineral density and say these findings have important implications when it comes to recommending weight loss programmes for middle-aged adults, who may already be at increased risk for bone fracture. They suggest that exercise should be an important component of a weight loss programme to offset the side effects that reducing calories can have on bone strength.

WLR says:

Before ditching your diet, let’s put this study into perspective.

To start off with, it only included a small number of people and so the results need to be interpreted with care. A lot more research is needed to confirm the findings of this study. And let’s not forget, that ultimately the researchers are recommending the same as other health professionals – and that’s to include exercise as part of a weight loss programme.

Ultimately, the participants exercised, on average, six times a week for around one hour each time to burn off an extra 320 calories daily. The researchers recognise this is a lot of exercise to expect people to do and so say a more practical approach is to combine exercise with a reduced-calorie diet.

This study serves to remind us of the importance of doing everything we can to keep our bones as strong as possible, for as long as possible, regardless of whether we’re trying to lose weight or not.

A severe reduction in bone mineral density increases the risk of osteoporosis, a condition where the bones become so weak they are prone to fracturing easily. Osteoporosis currently affects half of all women and one in five men over the age of 50 in the UK. In particular, it’s well known that body weight affects bone strength – in general, being underweight is one of many risk factors for osteoporosis. In contrast, it’s well established that weight-bearing exercise such as walking, running and aerobics can help to keep bones strong, therefore reducing the risk of osteoporosis.

It’s also important to eat a healthy diet that contains plenty of bone-strengthening calcium-rich foods, especially during childhood, the teenage years and early adulthood, when bones are still growing and gaining strength.

Reduced-fat dairy foods such as skimmed milk, fat-free yogurt and reduced-fat cheese are amongst the best sources of calcium – explaining why it’s so important to include three servings daily, especially when you’re trying to lose weight.

The National Osteoporosis Society recommends paying attention to other aspects of your diet and lifestyle as follows:

• Don’t eat too much protein – excessive amounts may upset the acid balance within the body, which then takes calcium from the bones to neutralise it. As a guideline, stick to two servings daily.
   
• Avoid salt and eat fewer salty foods – high levels of sodium (one of the main components of salt) can increase the amount of calcium the body gets rid of in the urine.
   
• Limit fizzy drinks – these often contain phosphate, in the form of phosphoric acid, to improve the flavour of fizzy drinks. Although more research is needed, it’s thought that too much phosphate can cause the body to lose calcium.
   
• Cut back on caffeine – a high consumption of caffeine could affect the balance of calcium in the body. Try adding milk to your coffee to counteract this effect or limit your intake to no more than two cups a day.
   
• Don’t smoke and only drink alcohol in moderation – smoking and drinking excessively are known risk factors for osteoporosis.