Many people assume that weight is mostly a matter of willpower -- that we can learn both to exercise and to avoid muffins and Gatorade. A few of us can, but evolution did not build us to do this for very long. In 2000 the journal Psychological Bulletin published a paper by psychologists Mark Muraven and Roy Baumeister in which they observed that self-control is like a muscle: it weakens each day after you use it. If you force yourself to jog for an hour, your self-regulatory capacity is proportionately enfeebled. Rather than lunching on a salad, you'll be more likely to opt for pizza.
Now, obviously that's not true for everyone, and Sarah and I gabbed this morning about how exercise actually makes both of us crave healthy foods -- fruits, veggies, water. But I have noticed that when I've exercised hard -- I'm starving -- I could pour food down my gullet with abandon if I'd let myself. That's not to say we shouldn't exercise; quite the contrary, says Time:
In addition to enhancing heart health and helping prevent disease, exercise improves your mental health and cognitive ability. A study published in June in the journal Neurology found that older people who exercise at least once a week are 30% more likely to maintain cognitive function than those who exercise less. Another study, released by the University of Alberta a few weeks ago, found that people with chronic back pain who exercise four days a week have 36% less disability than those who exercise only two or three days a week.
And of course, it's a good deal more complicated than that, even -- the equation for a healthy life will be recalculated time and time again. In the meantime I've worked up a sweat just thinking about it. I'm going to have one of Sarah's blondies.