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Preventive Medicine Column March 5, 2010 One Cookie, More or Less

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Preventive Medicine Column

March 5, 2010

One Cookie, More or Less
A recent piece in the Health section of the New York Times by Tara Parker-Pope raised questions about the impact of small steps, such as cutting out one cookie daily, on weight control.  The article makes the body's compensation for small caloric deficits into something of a mystery, but it is, in fact, well understood.  Here’s my take on the one-less-cookie approach to weight control.

Obesity in the modern world is much like global warming; both are by-products of almost everything we do, everything that makes modern living...modern.  The 'one less cookie' approach is to weight control what shorter showers are to climate control: a drop in the bucket.  They point in the right direction, but they are opposed by a colossal flow of forces in the opposite direction.  It's not that they are unhelpful, it's simply that unless the entire 'current' is reversed, they are insufficient to oppose it.

We need invoke no mystery to account for our bodies’ tendency to compensate for small reductions in caloric intake. I trust it's self-evident that a mouse needs fewer daily calories than an elephant- no one would even think to question it or ask why.  But...why? 

Is it because the mouse (or hummingbird) has a lower metabolic rate?  In fact, quite the opposite; some very small animals have stunningly high rates of metabolism.  Hummingbirds, in fact, must eat almost continuously or die, their metabolic rate is so high.  But they still need far fewer calories than elephants each day for the most obvious of reasons: they are a lot smaller.  Calories sustain mass, and it takes fewer calories to sustain less mass, more calories to maintain more. 

When we cut calories and lose weight, we...shrink.  That's what weight loss means.  As we shrink, we have less mass.  Less mass means fewer calories are required to maintain that lesser mass. 

When the current calorie intake matches the calories required to maintain the new, reduced mass- weight loss stops.  Ditto with weight gain.  Not some mysterious compensation- just the most obvious of relationships between energy and matter.  Calories are energy, bodies are matter.  Larger bodies require more calories to stay larger; smaller bodies require fewer calories to stay smaller.

Saying that small changes don't help with weight control is a bit like saying one sock, or mitten, won't help very much to keep you warm on a winter day. 

For one thing, it's true.  If you are not dressed warmly overall, a single sock or mitten won't help a lot.  However, if you are reasonably dressed, the addition of that mitten will certainly help. 

But the bigger issue is this: putting on one mitten will certainly NOT make you one iota warmer if at the same time, you take the other mitten off.  The big problem with 'eat one less cookie' approaches to weight control is one-less-cookie-now very easily results in 12-more-French-fries-later, or an extra soda, or...whatever.  We don't track our food intake reliably enough, without a great deal of out-of-the-ordinary effort, to make sure 'one less cookie' actually removes those cookie calories from our diet, and replaces them with...nothing.  The natural tendency will be to replace them.

As for small doses of physical activity- they are a good thing for health, but may have minimal effect on weight because it is so easy to replace those calories.  We are fuel-efficient machines, and thus can readily take in more calories than we burn- especially in a world where tasty, calorie-dense foods are ubiquitous. 

When the energy balance math is done, people are inevitably disheartened to learn how much physical work is required to burn a meaningful number of calories, and how little eating can restore them all.  Alas, that's how it is.  Walking at a moderate pace, for instance, can increase metabolism by a factor of 4, so instead of burning 1calorie/min, you might burn about 4.

Now imagine that walk goes on for an hour. You will have burned 240 calories, 60 of which you would have burned at rest. Your net ‘gain’- nothing to sneeze at- is 180 calories. One large soda (or energy drink!), downed in a minute, can replace them all.

Were it not this way, we wouldn't be here, because our ancestors lived in a world where physical activity demands were enormous, and calories were in relatively short supply. In the modern world, however, this time-honored survival formula is a formula for exasperation.

My trademark metaphor for weight control- at both the population and individual level- is a levee. Every small, incremental contribution to the cause is a sandbag. 

No one sandbag will hold back the obesigenic flood-waters that sweep us along in the wrong direction, but on the other hand, the levee will never top the flood waters unless we do stack sandbags. 

So in my view, every little bit DOES help- but only if it's a little bit of something bigger.  And only if it's a little bit that is not undone by a corresponding bit in the other direction.  Skip a cookie, eat more cake is a 'stack one sand bag, take one away' scenario; so is an 'I exercise more, so I can eat more' approach. If you adopt these strategies, expect to stay wet for the foreseeable future.

But small steps matter if they add up, and consistently go in the right direction.  Sandbags work when they add up to a levee that tops the flood.  This is true in protecting your body from weight gain, and in protecting the body politic from epidemic obesity.

One more cookie didn’t get us into this mess; one less cookie won’t get us out. But it’s a start.

Dr. David L. Katz;

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