Wednesday Bubble: protein, weight and bones – keep it in balance

Posted by Liz on Aug 4, 2010 in bone health, diet | 1 comment

Weight loss improves health, right? Well, yes, and no. Because it turns out that weight loss also increases the rate that the bone loses density, so in midlife and menopause, weight loss can be a double-edged sword.

In two recent studies published in the online edition of the Journal of Gerontology, researchers are reporting that women already at risk for osteoporosis due to their age and menopausal status may want to pay attention to what they eat when they try to lose weight. In fact, consuming large amounts of protein derived primarily from animal sources, e.g. lean meats like pork, beef and chicken, may negatively impact bone density and in turn, further increase osteoporosis risk.

Here’w what you need to know:

• In the first study, women between the ages of 43 and 80 reduced their daily caloric intake by 750 calories. Over three months, about half of the women ate meat-free diets that derived about 18% of their daily protein from vegetarian, dairy and egg sources and other half, ate diets comprised of about 30% protein derived from lean pork.

• In the second study, women between the same ages consumed about 1,250 calories a day in five meals over nine weeks. While the bulk of these calories were from a vegetarian diet, women were asked to eat either 250 calories of carbs daily (shortbread cookies, sugar coated chocolates), chicken (plus 10 grams of butter) or the equivalent in fat/saturated fat but as beef.

• Although women in the first study lost about the same amount of weight (~19 lbs), those eating animal protein has a 1.4% greater loss of bone mass. Likewise, in the second study, all the women lost weight but those women eating animal protein sources lost significantly more bone mass compared to women eating carbs.

• Women in both of these studies were considered overweight or obese based on their body-mass indices (BMI).

Importantly, many of the today’s popular diets for weight loss (e.g. South Beach, Atkins) emphasize increased intake of protein over carbohydrates (although the former also emphasizes good versus bad (i.e. glycemic index) carbs. What this means is that while you are cutting back, you may also be losing more bone mass than you normally would with weight loss.

Consequently, one of best approaches for women who are going through menopause and trying to keep the weight off may be to increase the daily  amount of so-called “good fats,” which as my friend Mollie Katzen, suggests should include nuts, avocados and fatty fish like salmon. Many of these foods are also good sources of protein and while not necessarily working to build bone, may stave off bone mass loss while you are trying to lose a few pounds or maintain your current weight.

At the end of the day, it’s all about balancing the good, the bad and the ugly. Our skeleton is fragile and it’s critical that we do all we can to keep it in one piece.

Want to learn more? I’ve dedicated several posts to osteoporosis, bone loss and bone health.