Exercise harder and eat less?

I'm back-pocketing the studies today, Nerd Herd. That's right, no science today, so put your slide rules back in your pocket protector and prepare for a yarn. Today, I'm going to get all anecdotal on ya. In honor of the Tour de France, I want to talk about a little theory I've formed around the relationship between exercise and appetite by telling you a little bit about my cycling habit.

But the best way to preface my tale is with a study.

Bwah bwah bwaaah! Burn on you! You totally thought you wouldn't have to take notes today, right? No way. This is The Nerd. Of course there are going to be studies! (But I am going to bring this back to a story about me eventually, so sit tight.)

Today's study, appearing in the International Journal of Obesity, is tiny and therefore not super conclusive, but it's interesting nonetheless. 17 overweight men were split up into four groups (which bothers me because 17 isn't a multiple of four, but whatever). Each smaller group of four, five, or 4.25, I guess--was assigned 30-minute exercise routines of varying degrees of intensity. Moderate cardio, hard high intensity interval training (HIIT), super hard HIIT, and no exercise at all. Here's the cool part: the guys who did HIIT ate less the next day. In other words, exercise may actually help suppress hunger. And because these were overweight people, I don't think it was "starving in the desert... going to eat my shoe" hunger. I think it was plain, ol' shitty eating habits hunger.

Although small, the study is comprehensive and super-geeky. They tested the participants out the wazoo and found, among other things, that the super HIIT guys had lower active levels of ghrelin, a hormone produced mainly by the stomach and pancreas that stimulates hunger. They also found that blood glucose levels were higher. I'm not sure why, but I'm guessing that it has to do with the body better processing existing energy stores. And one other thing, the HIIT guys enjoyed their workouts the same at the cardio guys. In other words, harder exercise didn't suck more.

So that's the study. Now let's talk about me. I've been a committed exerciser for decades now, but as many of you know, I took up cycling recently and it's completely redefined my relationship with my body. For example, I've noticed that on riding days, my hunger is insane. Because my body needs to replace the glycogen and sodium I lose on long rides, I crave salty and sweet foods, but I'll pretty much eat anything. If I can chew it, I want to eat it. I should get a t-shirt made to wear those days that says, "You gonna eat the rest of that?"

It's not surprising, from a physiological point of view. In addition to all the sodium you lose on a hard ride (about 1000-2000mg an hour), you burn through crazy calories while road cycling. For example, yesterday I rode two hours, covering 33 miles and 2690 feet of climbing. According to Strava, my estimating caloric burn was 1500 calories. In two hours, I burned more than many dieters eat in an entire day.

So I eat a lot, which is kind of weird, given I have a history of overeating. I was a chubby kid who regularly ate Cap'n Crunch until my gums bled. For the most part, keeping my eating under control is a daily struggle. Cycling has completely shifted that. There's a great passage from the book Bike Snob that sums it up well.

Once you start riding you're no longer one of the sedentary masses. Also, you won't need to eat less. Actually, you'll need to eat more. Food will no longer be an indulgence. It will become what it was always actually supposed to be, which is fuel. Your meals will be sources of energy, not guilt. 

But here's the rub. While I'm pretty much just a stomach, a mouth, and a pair of legs on cycling days, I find that I'm less hungry on non-cycling days than I can ever remember being. I have my three squares, maybe an apple or something thrown in the middle, and I'm all good. My emotional eating seems to have been curbed.

I think this is exactly what those fat guys doing half an hour of HIIT in the study are experiencing. Most of us know hunger as a cue sent from a goulash of imbalanced hormones and scores of repressed physiological issues tucked deep into the folds of our sadly mis-managed gray matter. When you exercise hard, you're faced with real hunger--the genuine need for food as fuel. It is my postulation that when faced with healthy hunger, your emotional hunger starts to feel less oppressive. Furthermore, exercise stimulates the release of "feel good" endorphins in your brain, which also happens when you eat sugar, so you're less hungry because you're already getting all the benefits of eating Twinkies, without having to deal with pesky annoyances like diabetes, obesity, cancer, and heart disease.

And this study shows that you don't need to spin your wheels for hours every day to invoke that change. Suddenly, jumping around for 30 minutes a day makes a lot of sense.

Cool, huh?