Eating Your Macros Without Gaining Weight

The morning after I announced my grand plans to run a 10k, I awoke to a raging case of STREP THROAT. Positive Health Wellness I rushed over to the hospital for a timely strep test and began the 10-day course of penicillin. By the last couple of days, I actually felt well enough to start jogging slowly on the treadmill.

The idea of a race sounds so much better than the actual training process. I didn’t really think that training would be a sacrifice, but even last night (on a Friday!) I had to rush home after work to get some running in. I guess I underestimated how far behind I’d be after such a lazy winter. Good thing I love a challenge.

Being partial to my profession, my first course of action was putting together a training diet. At UConn, I had the very cool opportunity to work with Dr. Nancy Rodriguez (dietitian for the UConn athletes). During those few weeks I got a glimpse into the world of sports nutrition and what’s really required for training– specifically, the function of carbs for endurance & protein for recovery.

There are three essential macronutrients: carbohydrates, protein and fat. Using myself as an example (5’8”, 140 lbs), the baseline for maintaining my weight without exercise = 1800 calories/day. A standard “balanced diet” breakdown = 60% of calories from carbs, 15% from protein and 25% from fat. I assumed my current running routine was in the “light to moderate” training category. The duration of my “run” is no more than 30 minutes and a portion of that is spent jogging/walking. Not exactly 10k yet…but I’ll get there.

According to The Academy of Nutrition and Dietetics, the macronutrient guidelines for “light to moderate” running are as follows:

Carbohydrate Needs: 2.3 – 3.2 grams per pound of body weight. I averaged this to 2.75 grams x 140 lbs = 378 grams of carbohydrates per day. Because carbs have 4 calories per gram, this = 1512 calories from carbs. Stay with me now…

Protein Needs: 0.55 – 0.8 grams per pound of body weight. I averaged this to 0.68 grams x 140 lbs = 95.2 grams of protein per day. Because protein also has 4 calories per gram, this = 380.8 calories from protein.

Hmmm, this means 1512 carb calories + 380 protein calories= 1893 from carbs and protein alone. Based on the numbers, I’m already over my calorie budget without taking into account dietary fat. Fat has 9 calories per gram and is not a negotiable nutrient (unless you live off SnackWell’s fat-free cookies). Since I’m running, I should be able to afford some extra calories for fat. But how many?

According to Runner’s World, if I run 3 miles in 35 minutes (jogging/running/walking an average 11:40 min/mile) I’ll burn 318 calories. Gotta admit, I was a little disappointed by this number considering all the wheezing and sweating that’s involved. Guess the saying holds true, “You can’t outrun your fork.”

Therefore, I should have (1800 + 318) 2118 calories/day when I exercise. This equals out to only 10% of my total calories for fat based on my first carb/protein calculation. What’s a dietitian to do?

I played with numbers a little more and found that the lower end of the carb & protein guideline works out much better for me. Perhaps my workouts are not as “moderate” as I thought. At 2.3 grams of carb/pound of body weight + 0.55 grams of protein/pound of body weight, I totaled out to 1596 calories from carbs + protein. This left me 552 calories for fat, exactly 25% of my total!

The reason I dragged you through this mathematical journey was to explain the risks of taking macronutrient guidelines at face value. Guidelines from REPUTABLE sources are a great starting point. Exercise is really hard, especially for beginners. Its so easy to overestimate how much nutritional cushion you actually need.

If I blindly followed my initial protein calculation, I would have either:

1. Gradually gained weight from excess calories or

2. Had to compensate by under-eating carbs or fat– both of which play very important roles in training.

Always use guidelines within the context of your total intake. Most foods are a mixture of carbs/protein/fat so the grams accumulate more quickly than we sometimes realize. When in doubt, call a registered dietitian to do the math for you!

To keep track of my intake, I set-up a new account on MyFitnessPal. I’ve always been a fan of MyFitnessPal because its a (free) and easy way to get a clear picture of your diet. Feel free to add me (anastasiadietitian) and check out how these calculations translate to my everyday food diary. Its actually not as complicated once you start living it.