We all know you’re supposed to exercise and eat a balanced diet, but if you only had the willpower to do one, what would be better for your body?

I friend of mine posed this question recently, and I’m not afraid to admit I didn’t really know the answer.

That’s not a bad thing, actually quite the opposite. The moments you feel lost, are the moments you know you’re about to learn something.

So I turned to the greatest minds of science. Einstein, though a little strange in regards to his love-interests, brought a refreshing sense of perspective to the world of physics. He didn’t try to follow the same lines traced by countless physicists before him, but tried to picture the universe from his point of view. These are now famously know as “thought experiments”.

So the easiest way to answer this question, I think, is to picture a set of completely average twins, a thought experiment of our own.

Meet Skinny and Toned

We start with two identical twins. Same genes, same build.

But fundamentally different. See…

Skinny refuses to exercise, but is good with self control. Give him a diet and a nudge and he’ll have no problem following it.

His brother Toned, REALLY loves food, especially pudding. The word “diet” is like nails on a chalkboard, but the word “gym” causes him to perk up quickly.

So after 50 years of this, which one is better off? That is the ultimate question.

You’ve probably seen the infamous “Super Size Me“, the documentary that set the nations regard for McDonalds to flame. While I don’t think it was 100% honest journalism, I think it’s good for showing that much of your energy, mental or physical, comes from the foods you consume.

What I’d like to point out, is the highly touted diet of Olympian Michael Phelps.

Supposedly 12,000 Kilocalories, full of things like poptarts and toasters strudels, energy drinks, 1lb of pasta for dinner, and 5-egg omelets. It seems that an elite athlete should be watching his intake  more than the average individual. But most evidence points to the opposite. It’s not uncommon to see the fastest humans consume things like energy drinks or Usain Bolt tossing back chicken nuggets on the day of competition.

Point for the Exercise camp.

Then again, most studies in life-extension involve what’s known as caloric restriction. This isn’t malnutrition mind you, but getting 100% of your daily needs of vitamins and minerals, with only 70% or so of your typical calories.

Age for mice on calorie restriction

Point for the Diet group.

Then we have to think of the psychological impact. If you’re eating poorly, you might have a hard time moving much in the first place. You may have more fatigue at work, or less energy to go on a Friday-night date. If you eat poorly in the first place, you may not have much motivation to exercise. If you diet too much, you too may not have enough energy to exercise, or even perform basic day to day functions.

You probably hate this saying as much as I do by now but “Moderation” is without a doubt a staple of nutrition.

If I were to pick just one, I would pick the Michael Phelps/Usain Bolt style of diet.

Not necessarily because it’s “better” for you, but because they seem to function at a high level, stay fit, and  enjoy the foods they get to eat. I had a teacher once say “at that high of an activity level, it almost doesn’t matter what you’re eating as long as you get enough”. I think that’s a bit simplified, but shows that in some instances, total caloric intake trumps absolute nutrient value.

Take a step into Clinical Nutrition and you’ll see this all the time, burn victims need almost twice as much protein and calories as normal, and the rest is all but worthless unless you can meet these needs.

Exercise, in all likelihood, trumps diet.  But humans don’t live in a thought experiment. Diet affects energy level, which affects willpower, and our ability to exercise. Eat to live, live to move, move to eat.

At least, that’s my motto.

Be good to each other.

– Joshua Iufer, RD