Don't Spare the Protein

To anyone trying to lose weight, avoiding the virtually obligatory reduction in lean body mass is always a challenge. Not only does "offloading" as the body gets lighter reduce the actual "weight-bearing" work resulting in loss of muscle mass, but also the fact that most dietary recommendations tend to also reduce protein intake to maintain a "balanced" diet can promote a protein catabolic state.

As skeletal muscle is a major determinant of energy expenditure, losing muscle mass eventually limits the amount of weight that can be lost at any given caloric deficit, resulting in an early plateau. Furthermore, as lost lean body mass tends to be replaced with fat during weight regain (catch-up fat), you end up with a greater fat mass than before your diet.

The importance of maintaining protein intake during diet-induced weight loss was again illustrated in a recent study by Melanie Bopp and colleagues from Wake Forest University School of Medicine, Winston-Salem, NC, published in the Journal of the American Dietetic Association.

The authors investigated the association between dietary protein intake and loss of lean mass during weight loss in postmenopausal women through a retrospective analysis of a 20-week randomized, controlled diet and exercise intervention in women aged 50 to 70 years. Weight loss was achieved by differing levels of caloric restriction and exercise. The diet-only group reduced caloric intake by 2,800 kcal/week, and the exercise groups reduced caloric intake by 2,400 kcal/week and expended approximately 400 kcal/week through aerobic exercise.

Lean mass was measured using DEXA. Average weight loss was 10.8+/-4.0 kg, with an average of 32% of total weight lost as lean mass. While protein intake averaged 0.62 g/kg body weight/day (range=0.47 to 0.8 g/kg body weight/day), participants who consumed higher amounts of dietary protein lost less lean mass. These associations remained significant after adjusting for intervention group and body size.

The authors conclude that inadequate protein intake during caloric restriction may be associated with adverse body-composition changes in postmenopausal women.

I would dare to add that the same is probably true for anyone undergoing a dietary weight loss intervention that does not maintain adequate protein intake.

AMS
Edmonton, Alberta

I'll Take Catch-Up With Those Fries

Yesterday, I attended the "Crosstalk" symposium at ECO 2008 here in Geneva.

Once again, I was fascinated by Abdul Dulloo's (Co-Chair of the Symposium) talk on the phenomenon of "catch-up" fat.

Simply stated, this phenomenon describes the preferential accumulation of fat tissue as part of any weight-gain process that follows an energy deprived state (See Dulloo's excellent 2008 review for more on this topic).

Interestingly, this phenomenon occurs irrespective of whether the energy-deprived state is caused by voluntary or enforced starvation, dieting, anorexia or severe illness including sepsis or cancer.

In fact, it even occurs in small-for-gestational-age babies, who manage to rapidly make up for their low birth weight by rapidly tucking away those calories in those chubby fat depots.

Even more interestingly, data suggest that the excess calories that are tucked away are only partly derived from increased caloric intake. Most of them come from preferential partitioning of energy to the fat stores, largely by dramatically turning down skeletal muscle thermogenesis.

This means than even if you are careful not to "overfeed", your lean tissue will happily deprive itself for the benefit of those fat depots.

In animal experiments, high-fat refeeding appears to make this phenomenon even more pronounced.

All of this appears to be related to substantial insulin resistance that occurs during this "regain" phase and researchers are still trying to figure out what exactly makes the muscle "slow down" in order for the fat to accumulate.

Teleologically all of this makes sense. The idea perhaps is to rapidly take up those calories (following the famine or illness) and store them away - let's worry about rebuilding the lean mass later.

Unfortunately, at least in animals, this process may be detrimental in the long term. There is now a fairly consistent body of evidence that shows "catch-up" growth to be a risk factor for the development of cardiometabolic risk factors including abdominal obesity, type 2 diabetes, and dyslipidemia - all eventually leading to heart disease.

As regular readers may recall, I recently blogged about the apparent increased risk for the metabolic syndrome with weight cycling - perhaps a reflection of this phenomenon.

Whatever the causes and consequences of catch-up weight, the phenomenon is very real - people tend to get fatter with every diet; patients recovering from cancer tend to put on massive amounts of fat when they recover - most interesting indeed.

What if abdominal obesity is not a consequence of overeating alone but rather a result of past deprivation?

I guess I was not too far off the mark, when the New York Times recently quoted me as saying,"You might want to focus on being as healthy as you can and not obsess about your weight”.

Certainly no point losing weight if it just comes back as fat - i.e. unless you seriously believe you can keep it off by sticking to your weight management strategy for life!

AMS
Geneva, Switzerland