Many popular diets—including those that are popular among runners—are based on the idea that you have to balance your nutritional energy sources (carbohydrate, fat, and protein) perfectly in order to stay lean and healthy.
They just can’t agree on what that ideal balance is. Some say we should get no more than 20 percent of our calories from fat. Others say we should limit our carb intake to 10 percent of total calories. The Zone Diet recommends a precise ratio of 40 percent carbs, 30 percent fat, and 30 percent protein. Who’s right?
They’re all wrong. Science clearly indicates that there is no perfect balance of nutritional energy sources. Humans are metabolically very adaptable.
We can thrive on a variety of diets. What’s important is that we get enough of each energy source and not too much total energy (i.e. calories), and also that most of our carbs, fat, and protein come from natural, whole foods.
Let’s take a closer look at the specifics.
Carbohydrate is not an essential nutrient so we can get by on very little of it. However, it’s also the body’s most powerful energy source, so the more active you are, the better you will perform with higher levels of carb intake. If you do just a handful of short workouts per week, a low-carbohydrate diet is perfectly adequate.
If you are a serious racer who often works out twice a day, you may need to two or three times as much carbohydrate to get the most out of your training. As a rule of thumb, I suggest starting at a baseline of 3 grams of carbs per kilogram you weigh (1 kg = 2.2 lbs) and adding 1 g/kg/day for every 20 miles you run per week.
The healthiest high-carb foods are fruit, whole grains, and dairy. Refined grains and foods with added sugar should be eaten sparingly. The World Health Organization now recommends that consumption of added sugars be limited to 25 grams per day.
A healthy diet can be anywhere between 20 percent and 40 percent fat. More important than the amount of fat you eat is the types. Most of us don’t get enough of the essential omega-3 fatty acids EPA and DHA. The best source of these nutrients is fatty fish such as salmon. Make sure to eat it at least a couple of times per week. If you don’t eat fish, take an omega-3 supplement. Aim for a total of 1 to 3 grams of EPA and DHA daily.
Avoid overdoing saturated fat, especially from red meat. This type of fat is fine in moderation, but moderation means less than 10 percent of your total daily calories. Worse than saturated fat are the artificial trans fats. Try to avoid these entirely.
A little protein goes a long way. Research suggests that about 1.2 gram of protein per kilogram (1 kg = 2.2 lbs) of bodyweight per day is plenty for runners. So if you weigh 150 lbs (68 kg), aim for about 82 grams of protein daily. If you train heavily, eat a little more. Also eat a little more protein (about 10 percent) if you’re a vegetarian, as plant protein is not absorbed as well as protein from animal foods.
One Size Doesn’t Fit All
There are lots of diet gurus out there trying to convince us that there is only one way to eat for maximum health and fitness. Tune them out. You can be healthy and fit on almost any diet that fits your preferences and lifestyle provided it respects the general guidelines for balancing your energy sources that I’ve just outlined.