The Ultimate Guide to Weight Management for Runners

Matt Fitzgerald
by Matt Fitzgerald
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The Ultimate Guide to Weight Management for Runners

Most runners share the same basic goals of getting fitter and performing better. But many runners also have a goal to lose weight. There’s nothing wrong with either of those goals. It’s pursuing both of them simultaneously that’s a problem.

Simply put, runners cannot successfully pursue maximum fitness and aggressive weight loss at the same time. That’s because the eating patterns and training practices that are most effective in building fitness are different from those that work best to shed excess body fat. To get the best results from your diet and training, you need to choose the one goal that’s most important to you now — fitness or weight loss — then eat and train accordingly until you’re ready for a new goal.

Of course, some dietary rules and training practices apply at all times. For example, regardless of what your goal is, your diet should include a variety of natural foods and limited amounts of processed ones. But when it comes to calories, macronutrients, intensity balance and strength workouts, what works best for building fitness is very nearly the opposite of what works best for weight loss.



Recently I was contacted by a young female runner whose half-marathon training was going terribly. She felt heavy-legged in every workout and wasn’t seeing any improvement in fitness, despite being quite consistent in her training. I asked a few questions about her diet and learned that she was limiting herself to 2,000 calories per day, just as she had done before she started ramping up her workouts.

As this example illustrates, when you’re training hard to improve your fitness, it’s essential that you eat enough to enable your body to meet the energy demands of your workouts. The consequences of not doing so include poor workout performance, inadequate recovery between workouts and increased injury risk.

The most successful runners don’t impose inflexible calorie counts or portion-size limits on themselves when they are training for maximum fitness. Instead, they listen to their bodies and eat enough to satisfy their true energy requirements as expressed through physical hunger (versus “hedonic” hunger, or the desire to eat just because something looks good).


Losing weight, of course, requires that you eat fewer calories than your body burns each day. So when weight loss is your top priority, it’s a good idea to estimate your energy expenditure and count the calories you eat to ensure that you end each day with a deficit.

The optimal deficit is 300–500 calories per day. If you eat any less, persistent hunger is likely to make you miserable. Additionally, larger calorie deficits result in less fat loss and more muscle loss. In a study performed at Rockefeller University, one group of subjects cut their energy intake by 700 calories a day, while a second group cut their energy intake by 300 calories a day. The first group lost more total weight, but it was only 48% fat — the rest was lean body mass. Meanwhile, the weight lost by the second group was 91% fat.



The best runners in the world come from Kenya. The typical Kenyan runner gets 76% of his or her daily calories from carbohydrates. Elite runners in other parts of the world also eat a lot of carbs. The reason is simple: The more you train, the more carbs you must eat to get the maximum possible benefit from training.

In recent years, some runners and other athletes have experimented with low-carb diets, but such eating habits just don’t measure up. In a 2014 study, Polish researchers placed a group of mountain bikers on two diets — low-carb and high-carb — in random order for four weeks each. After four weeks on the low-carb diet, their VO2 max and time-trial performances were significantly lower than they were after four weeks on the high-carb diet.

As a runner, you don’t have to get three-quarters of your calories from carbs as the Kenyans do. You should, however, include high-quality, carb-rich foods such as whole grains, fruit and dairy in all of your meals and most of your snacks.


In the Polish study described above, subjects lost not only fitness but also body fat on the low-carb diet. Many studies have shown that low-carb diets are effective for weight loss, but the latest evidence suggests that it’s not actually cutting carbs that stimulates weight loss. Rather, it’s increasing protein intake, as most people do automatically when they cut carbs.

A high-protein diet helps weight loss in a couple of ways. First, it increases satiety, so you eat less. In a study performed at the University of Washington, overweight women whose protein intake increased to 30% of total calories ate 441 fewer calories per day. These women didn’t make any conscious efforts to eat less; the additional protein made them feel fuller. In addition, a high-protein diet increases resting metabolism, so your body burns more calories throughout the day.

When weight loss is your top priority, try to get about 30% of your daily calories from high-quality protein sources such as fish. But as soon as your goal switches to building fitness, you’ll want to slash your protein intake roughly in half. Animal studies suggest that a high-protein diet inhibits fitness building by blunting certain beneficial adaptations to cardio training.



Intensity is one of the most fundamental variables of training. It can be defined simply as how hard you’re working at a given moment relative to your personal limits. Different workout intensities carry different benefits. To get the best possible results from training, runners must balance the various intensities in a way that combines these benefits optimally.

Research has shown that world-class athletes in endurance sports, including elite runners, spend approximately 80% of their total training time at low intensity (60–77% of maximum heart rate) and the remaining 20% at moderate intensity (78–91% of max HR) and high intensity (92–100% of max HR). More recent studies suggest the same intensity balance is also optimal for recreational runners. In a 2014 study, Spanish and Norwegian researchers found that recreational runners who followed the 80/20 rule for 12 weeks improved their 10K race times twice as much as runners who did only half of their training at low intensity, as most recreational runners do.

An additional advantage of training mostly at low intensity is that it allows a runner to run a lot, and running a lot is beneficial in its own right. The more you run, for example, the more efficient your stride becomes.


The optimal training program for fat loss is the inverse of the optimal training program for fitness development. This was shown in a 2014 study conducted at the University of Salzburg. Endurance athletes were separated into four groups, each of which trained for nine weeks at different intensities. The group that showed the most improvement in fitness was the one that came closest to the 80/20 rule. But the group that lost the most body fat was the one that did more than half of its training at high intensity.

Other research has yielded similar findings. Therefore, while high-intensity interval training should have a small place in your program when you’re preparing for races, it should dominate your weekly workout agenda when your primary goal is fat loss. But because high-intensity exercise is much more stressful than low-intensity exercise, the overall volume of training you do in these periods should be relatively low.



Strength training, which encompasses weightlifting, calisthenics and other forms of resistance exercise, is proven to enhance running performance. One recent study found that eight weeks of strength training improved 10K race performance by 2.5%.

There is also some evidence that strength training reduces the risk for common overuse injuries such as knee pain. Studies have shown that runners who suffer from knee pain have weak hip abductor muscles. Strengthening these muscles may help prevent this type of injury.

In order to maximize the performance-enhancing and injury-prevention benefits of strength training, runners need to take a functional approach to this type of exercise. This means basically doing exercises that are relevant to running and avoiding those that aren’t. Walking lunges are relevant to running because they mimic the stride action. Classic bodybuilding exercises such as biceps curls, on the other hand, will do nothing for you as a runner.


If your main concern is shedding excess body fat, then your primary objective at the gym is not to add power to your stride or strengthen weak stabilizer muscles but to gain muscle mass. Adding even a couple of pounds of lean muscle to your frame will increase your resting metabolic rate so you burn more fat around the clock.

The best exercises for adding muscle mass are different from those that carry the greatest functional benefit for running. Movements that isolate individual muscle groups, such as machine leg extensions and barbell bench presses, are great muscle-builders but don’t lead to faster race times precisely because they work individual muscles in isolation — unlike running.

A muscle-building approach to strength training can, however, serve as good preparation for a functional strength program. The former will improve your all-around strength, enabling you to do functional strength exercises, like walking lunges, more effectively.

The other three fat-loss techniques we’ve discussed in this article will also set you up for success when you turn your attention to building fitness. A high-protein diet will enhance the muscle-building effect of strength training. High-intensity intervals will set you up to start race-focused training with a solid base of fitness. And, of course, a calorie deficit will allow you to start your race-focused training closer to your optimal racing weight, when used alongside the other three techniques. Just be sure to replace these methods with those that work best for building fitness when your main goal shifts.

About the Author

Matt Fitzgerald
Matt Fitzgerald

Matt Fitzgerald is a certified sports nutritionist and author of Diets Cults and 80/20 Running, among other books. He provides real-time audio coaching for runners and other athletes through and one-on-one nutrition coaching through


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