With age, people lose bone density, especially women after menopause.filmstudio/iStockPhoto / Getty Images
You’ve likely heard that cutting calories to shed excess weight can cause you to lose muscle along with body fat.
Research suggests that for a 10 per cent reduction in body weight, about 20 per cent of this will be lean mass, a consequence that can diminish strength, stamina and resting metabolic rate.
Eating extra protein together with resistance training can help preserve muscle during a calorie deficit.
There’s another unwanted side effect of a weight loss diet, though, that you might not be aware of: bone deterioration.
Now, new research shows that adhering to a specific calorie-reduced diet – a Mediterranean diet – combined with physical activity can prevent a loss of bone density in postmenopausal women.
Here’s a breakdown of the study, plus how Mediterranean diet foods support bone health.
About bone density, why we need to preserve it
Bone density refers to the concentration of calcium and other minerals in a given area of bone such as the hip, spine or neck. Higher bone density indicates minerals are more tightly packed, suggesting stronger bones that are less likely to break.
With age, people lose bone density, especially women after menopause. Having bone density that’s lower than normal, called low bone mass or osteopenia, increases the risk for osteoporosis and bone fracture, which can reduce quality of life, mobility and independence.
A calorie-reduced diet is thought to reduce bone density by providing fewer essential bone nutrients, altering levels of bone-building hormones, increasing fat deposits in bone stem cells and reducing muscle, which provides support for bones.
The latest research
The study, published this month in the journal JAMA Network Open, was an analysis of the PREDIMED-Plus trial, a randomized clinical trial conducted in Spain involving 6,874 older adults.
For the analysis, researchers investigated the effect of a calorie-reduced Mediterranean diet, combined with exercise, on bone density in 924 PREDIMED-Plus participants, ages 55 to 75, with metabolic syndrome and overweight or obesity.
Metabolic syndrome is defined as having at least three of the following risk factors: hypertension, high blood triglycerides, elevated blood glucose, low HDL “good” cholesterol and abdominal obesity.
Half the participants were assigned to the lifestyle intervention, which involved a 30 per cent calorie-reduced Mediterranean diet (equivalent to eating about 600 fewer calories a day), physical activity and counselling by dietitians.
Specifically, the lifestyle intervention group was encouraged to limit red and processed meats, butter, margarine, cream, sweetened beverages, added sugars, white bread and refined grains while emphasizing whole grains, vegetables, fruit, pulses, nuts and olive oil.
These participants were also asked to walk briskly for at least 45 minutes six days per week, do resistance training twice per week and practise flexibility and balance exercises three times per week.
Participants in the control group followed a Mediterranean diet without any calorie restriction; they were not given any exercise recommendations.
The findings, why they’re notable
Participants in the lifestyle intervention group lost an average of three per cent of body weight over the three-year trial. By contrast, the control group lost an average of 0.7 per cent.
Compared to women in the control group, those in the intervention group experienced a significant increase in bone mineral density over three years, especially in the lower spine. This protective effect was not seen in men.
To arrive at these findings the researchers accounted for other influential factors including age, smoking status, calcium and vitamin supplementation, sedentary time, use of osteoporosis medication and body mass index.
Previous clinical trials in older adults have shown that losing weight from diet alone, even one with adequate protein, calcium and vitamin D, causes a reduction in bone mineral density.
What’s more, combining exercise with a calorie-reduced diet has not always been shown to prevent bone loss in older adults.
This is the first study to report that a healthy calorie-reduced Mediterranean diet together with physical activity can help preserve bone loss in older women during weight loss.
This finding suggests that the type of diet you eat to lose weight matters when it comes to preserving bone density.
How the Mediterranean diet may benefit bones
The anti-inflammatory and antioxidant properties of key Mediterranean diet foods – vegetables, fruit, whole grains, pulses, fish, extra virgin olive oil – are thought to play a role in reducing weight loss- and age-related bone decline.
Fruits and vegetables, for example, are good sources of vitamins C and K, as well as beta-carotene, each of which appear to help maintain bone density.
Protective polyphenols in extra virgin olive oil have been shown to promote bone formation.
Omega-3 fatty acids and selenium in fish have also been shown to positively influence bone density.
Adherence to the Mediterranean diet may also shift the gut microbiome in a direction that promotes bone health.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on X @LeslieBeckRD
