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Thursday, May 15, 2008

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!

Geneva, Switzerland


Nana Gletsu said...

Very interesting -Arya, thanks for sharing the information. Is the weight gain thought to be as visceral or subcutaneous fat?

Arya M. Sharma, MD said...

Thanks Nana,

Turns out the fat gain in combination with high fat diet (at least in animals) is also visceral.

Human data on this issue is unfortunately scanty - seems like clinical researchers haven't really pounced on this problem with the necessary enthusiasm.