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Let me introduce myself. My name is Mark Sisson. I’m 63 years young. I live and work in Malibu, California. In a past life I was a professional marathoner and triathlete. Now my life goal is to help 100 million people get healthy. I started this blog in 2006 to empower people to take full responsibility for their own health and enjoyment of life by investigating, discussing, and critically rethinking everything we’ve assumed to be true about health and wellness...

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August 02, 2008

Calorie Restriction and Bone Loss

By Worker Bee

Skeleton X-RayIt can seem like a cruel contradiction: lose weight, lose bone mass. Lose a lot of weight and lose even more. (Rest assured there’s more to the story, but we continue….) A collaborative study involving researchers from the University of Kansas and the University of Missouri highlights the downside of weight loss by calorie restriction both during and in the months following weight loss.

Researchers examined protein markers of bone breakdown and formation in 37 obese, middle-aged adults who lost 20 percent of their body weight through a severe calorie-restricted diet. Protein markers, which are released during bone breakdown and formation, are used as indirect indicators of bone remodeling. During the 3-month weight-loss phase, bone remodeling was elevated, and bone formation and breakdown were imbalanced as a result of a low energy intake. After weight loss phase, bone remodeling remained elevated during the 9-month weight maintenance phase, but bone formation and breakdown appeared to be balanced.

via Science Daily

Though the bone breakdown and formation rate had hit a homeostasis, the researchers caution that “Rapid rates of bone remodeling, regardless of the balance of breakdown and formation, can increase bone fragility.” They add that those seeking to lose weight should consider adding weight-bearing exercise and make sure they’re getting adequate calcium.

Our reaction? Well, yeah. Weight-bearing exercise is absolutely essential for maintaining not just muscle mass but bone density. Bone density is not only influenced by how much weight the body senses it carried around but how much “work” the body senses is happening in the bone and muscle connections. Countless studies have confirmed this, and research out of Washington University School of Medicine in St. Louis highlights its “osteoprotective effect” in weight loss. Their study compared bone density (as measured by blood markers and dual-energy x-ray absorptiometry) in two groups of older adults, one of which lost weight through restricting calories and the other by exercise. Their results? Though the CR group lost some 2.2 % of bone density in fracture-prone areas like the lower spine, pelvis and femur, the exercise group showed no substantial change in bone density. Though both groups showed higher rates of bone turnover than the control group, the researchers indicated that the work of exercise, the “muscles pulling on bones” can “produce strains in the skeleton that stimulate new bone production.” The “exercise-induced mechanical strain,” they say is actually healthy and protective.

The Primal Blueprint isn’t about caloric restriction. Interestingly though, when people cut out the carbs, they’re surprised how much their calorie intake drops. (The same is true for lab animals: caloric restriction diets generally reduce carb calories more than any other macronutrient.) But it’s ultimately about how your diet complements your body’s natural functioning. As Mark has said in the past, the “success” of CR in weight loss probably has more to do with insulin mitigation than with sheer calorie reduction. Add to this picture an exercise routine that challenges the body’s physical structure and fitness in a natural, optimal way, and you’re going to see optimal health. And wouldn’t you know it? That includes bone health.

Thoughts? We’d love to hear your questions or additions to what these studies highlight.

Wei Flickr Photo (CC)

Further Reading:

Fat-Oxidation Damage Control

The Importance of Blood Sugar

Plants Preserve Muscle Mass

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13 Comments on "Calorie Restriction and Bone Loss"


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Yongho Shin
9 years 6 months ago

Wow, nice find! I knew that extreme weight loss (trying to lose 5 pounds in a week, for example) was dangerous, but I didn’t know that weight loss with LACK of weightlifting was dangerous. I’m glad I do my cardio and weightlifting at the same time. 😛

9 years 6 months ago

Eating fewer calories than your body “wants” causes all organs to starve in addition to fat and bone tissue. If your metabolic profile is such that you body “wants” to have a certain bodyfat percentage, it will fight to maintain that at the expense of your other tissues. The reason traditional dieting is so difficult is that your organs are starving.

The only way around it is to change your metabolic profile through a good diet and exercise. Weight loss through grain avoidance, carb restriction, and intense exercise can cause fat loss without starving your organs.

9 years 6 months ago

this is interesting to me:
the “success” of CR in weight loss probably has more to do with insulin mitigation than with sheer calorie reduction.

as Id say I DO NOT do CR but I do focus on insulin mitigation (who knew? I mean I did it for how I feel (more energetic. less moody/bloated) but didnt use those 2 words) yet eat as much as I want of protein and goodfat rich foods.

9 years 6 months ago

Great post, but I’ve been seeing research that it isn’t low calcium intake that affects the bones, as much as low blood vitamin D3 levels that keep the body from being able to use the calcium it gets.

Perhaps bone loss won’t happen under caloric restriction/intermittent fasting if D3 is adequately supplemented? (And apparently the RDA is ridiculously low — many people need 5000 IU of D3 a DAY to get to a blood level of 50.)

9 years 3 months ago

This Article is very useful to me, I dig it into writing.Thanks.

Bill King
8 years 11 months ago

Great post again mate. I think you’ve hit the nail on the head there. Losing weight doesn’t have to be hard ywet mose people fail to realize the basics

6 years 10 months ago
Bone remodeling HURTS! I just joined a gym and started lifting weights. I also have had a palatal expansion in my mouth for the past 6 months which is remodeling (stretching) my maxilla. After my weight lifting later that day i had the EXACT same pain in my bones as I’ve been experiencing in my head the past 6 months…no soreness in my muscles though until the next day. I could literally feel the bones response to all the pressure that has been done to them during lifting. The bone pain was mostly felt in the long leg and arm… Read more »
5 years 11 months ago
Hi Mark, I’ve got a scale that reports Bone Mass %. I’ve been living a primal lifestyle for 6 months and have had great success, dropping 28 lbs, from 200 to 172, great lipid improvements, more energy & better (feeling stronger) workouts than ever. The only marker that has me slightly concerned is this Bone Mass %. For several years through weight fluctuations 185-200 lbs my bone mass % always seemed to stick at 8.4%, but over these past six months I have seen a steady decline to 8.0%. Do you have any thoughts on this; should I be concerned.… Read more »
5 years 10 months ago

I wonder how a scale could tell bone mass%.

I don’t even understand how they tell fat/lean mass unless you put in your other measurements.

I’m not sure I trust those scales if everything is simply calculated by one number (weight). I find my weight # to be the least telling of all of them.

5 years 9 months ago

How many calories is meant by calorie restriction? I eat around 800-1000 a day and im full and satisfied, I also Crossfit 3 times a week. Everyone says that if you eat less than 1200 your putting your body into ‘starvation mode’. Im trying to lose weight, and so far I am.

5 years 9 months ago

I have the same question as Jess: how many calories is meant by calorie restriction? Thanks!

4 years 10 months ago
Please don’t yell at me or tell me I’m an idiot, because I already know LOL. But I have been on a hard CR/IF diet for 3 weeks now and have lost 6lbs. And this is purely diet based (I do no sort of workouts). So I’m on my 4th week and I just cannot ignore how I’m so tired and so fatigued. Needless to say, I probably lost muscle and bone density. How do I recover? I’m 19/F/5″2’/116lbs, and want to lose fat and keep muscle in tact. Also, I have no access to a gym. Please help me,… Read more »
4 years 8 months ago

Nina, click the Start Here button at the top of the page. You need to subscribe to the Primal Blueprint and follow the instructions in the PB Fitness ebook. Basically, you move around a lot at a slow pace, lift heavy things (for example, by doing a set of bodyweight exercises), and sprint every once in a while. No gym membership is needed.