In a 2006 survey conducted by Australian Runner’s World magazine, weight control was listed as the fourth most popular reason for running by 58 per cent of the respondents. Additionally, 87 per cent of the runners claimed they run because “it keeps me in shape” — the primary reason for them participating in the activity.

These figures should not be surprising: 60 per cent of Australians are either overweight or obese and many of us are concerned about it. When we look at the almost skeletal frame of elite runners, it certainly seems like running encourages leanness and would be an ideal method for losing weight.

For many years we’ve been told that exercise — and particularly running — is a powerful tool in any weight-loss program and should be considered an integral part of weight control.

When we look at running for weight loss, a number of questions arise. Just how effective is running for weight loss and weight control? Is it the panacea that will help you shed those excess pounds? How much running does it take to lose weight? Are there any better ways to lose and maintain your weight? What about the widespread belief that’s been circulating for decades among runners — that we burn as much after our workouts due to our elevated resting metabolism as we do during our workouts; is this true? You’ll be surprised at what the research has to say about these questions and may find yourself making some lifestyle and running adjustments after reading this.

How much running is needed to burn one kilo of fat?

The standard measure of energy contained in one kilo of fat is 32 kilojoules. So if you burn 0.672 kilojoules per kilometre (which is about average for a 70kg person) you’d have to run 47 kilometres to lose one kilo of fat. That’s assuming you keep your diet constant. In other words, you don’t take in more kilojoules to compensate for your increased energy demands.

It’s also important to realise there is a large individual variation in how we lose weight. Some nutritionists estimate that this variance may be 10 to 15 per cent due to differences in gender, ethnic origin, age and weight. These differences perhaps explain why some people lose weight with great ease while others struggle to drop just a few pounds.

Running versus the rest

First, let’s compare running with the other major aerobic activities to see how it weighs in on the calorie-burning sweepstakes. Here’s a ranking of the most common aerobic sports in descending order of calorie burn, biggest burners at the top.

Kilojoules burned per minute

Activity	Weight in kilos   47–52	Weight in kilos   57–62	Weight in kilos   72–77	Weight in kilos   82–90	Kilojoules burned per hour for a 72kg person
Running — 16km/h		65.94	78.5	105	5796
Stair running		65.94	73.92	96.6	5292
Running — 13km/h	43.68	49.98	59.64	72.66	4893
Cross-country skiing-moderate pace	55	63	74.76	81.48	4485
Lap swimming — vigorous		41.16	49.14	67.2	3624
Deep water running		41.16	49.14		3624
Stationary rowing — moderate		35.28	42	46.2	3078
Running — 10km/h		41.16	49.14	67.2	2956
Jogging — 8km/h	36.12	38.64	48.3	53.34	2898
Lap swimming — moderate speed		33.18	39.48	50.4	2898
Aerobics — step		28.56	38.44	58.8	2536
Elliptical trainer				46.2	2436
Bicycling — stationary moderate effort		28.98	34.44	46.2	2070
Bicycling — stationary 16km/h	23.1	26.46	32.76	34.86	1965
Stair climbing	24.78	28.14	33.18	36.96	1990
Walking — 6km/h	18.9	21.84	25.62	28.56	1537
Walking — 3km/h	10	11.76	13.86	15.12	831

 

Have a look at the right-hand column of the chart that shows how many kilojoules a 72kg person will burn in an hour of exercise. As you can see, you have to run (or do any other type of aerobic exercise) for a long time to burn significant numbers of kilojoules. For example, you’d have to run at 13km/h for one hour to burn 4893 kilojoules — somewhat discouraging (and definitely unfair) when you consider there are 4000kJ burgers out there that take only 10 minutes to eat!

The chart also shows the disappointingly modest number of kilojoules you burn when running at a moderate pace. From this, we can safely surmise that for a moderate running program to help with weight loss, you must run consistently (ie 5–7 days/week) to burn enough kilojoules to cause an overall kilojoule deficit.

A glance at the chart shows that running is a heavy kilojoule burner but, if you look at the fine print, you’ll see that if you want to burn large amounts of kilojoules, your running must be done at intense workout levels which are, sadly, well beyond the range of the beginner or overweight runner.

Beginners are simply not able to maintain the energy demands of training fast every day and will inevitably end up exhausted, sick or injured within a few weeks. Considering that most beginning (overweight) runners are only able to run for relatively short periods of time at a slow intensity, for only a few days/week, they are really limited to moderate training programs. Thus, high-intensity running is difficult, if not impossible, for beginners to stay with for effective weight loss.

Moderate exercise and weight loss

The results of studies that looked at moderate aerobic exercise are quite dismal. The best-designed studies fail to show that moderate aerobic swimming, cycling and running programs have a significant impact on weight loss. In fact, most researchers consider aerobic exercise a rather weak method of accelerating weight loss. A one-year study at Stanford University (King et al, 1991) found that 350 men and women, who did 3–5 exercise sessions lasting 30–40 minutes each, had no significant weight loss, although their aerobic fitness improved 5–8 per cent.

Many other studies (including two meta-analyses) conclude the same thing: moderate exercise is simply not enough to reduce bodyweight significantly (Garrow et al, 1995; Miller et al, 1997).

The fat-burning zone

A popular theory is that you need to work out long and slow to burn fat kilojoules. This theory posits that when you run at a slow pace for a long time you tend to burn fats as your primary fuel source. The theory is technically correct, because running at low intensity does tend to draw more from fatty acid fuels in your bloodstream than from carbohydrates (though both will be burned to a greater or lesser extent).

However, in practice your body ultimately cares only how many kilojoules you have burned in a workout. Your metabolism is not particularly concerned about the prime fuel source that you draw on, so it matters not what fuel you burn when you exercise. This is potentially shattering news to those hundreds of thousands of runners and fitness buffs who spend hour upon hour on roads and cardio equipment each day doing long, slow exercise. Does this mean you should stop doing long, slow running? Certainly not — long slow running clearly has its place in a healthy lifestyle — but perhaps you might consider some higher-intensity workouts to shake things up a little.

Indeed, some research shows you may be better off exercising at a higher intensity for a shorter period of time compared with exercising at a lower intensity for a longer period of time, because you burn far more kilojoules in the shorter time. If you’re strapped for time (and who isn’t these days?) this is good news indeed. Vigorous exercise also has another health benefit, according to some studies: it tends to preferentially draw fat from the abdominal area (Visser et al, 1997; Tremblay et al, 1990). Large deposits of abdominal fat are linked to a number of heart disease risks and other markers of poor health, so anything that reduces these fat deposits will make us healthier.

In light of this research, running long and slow suddenly does not seem so appealing or efficient. Besides, who has the time or interest these days to spend long hours on the road, treadmill or cycle, in the pool or on the elliptical trainer? So, unless you’re a serious distance runner cranking out an hour or more a day at a fast pace, you’re not going to find running very effective for weight loss.

Having established that we need to run at least one hour a day, six or seven days a week at a fast clip to burn substantial kilojoules, this would explain why there are plenty of thin distance runners. If you ask them about their training, they’ll tell you they run close to this amount, frequently at a fast pace. So, in effect, the volume and intensity of running required to lose weight is confined to elite runners and those with high levels of fitness.

There’s also a more insidious side-effect when starting up a running program to lose weight. People get much hungrier when they start running, so there is a tendency to eat more kilojoules to compensate, which of course negates the effects of the kilojoules burned from running. Many beginning runners complain that they actually put on weight when they start out. Other beginners may be so tired from their running program that they lie around for the rest of the day, ultimately burning fewer kilojoules because their metabolism is not being revved up periodically from daily activities such as walking.

Diet in weight loss

Researchers, discouraged by the poor results of exercise studies started looking at the diet and nutrition part of the weight-loss equation and found heartening news. Not surprisingly, study after study has found that reducing kilojoule intake significantly reduces weight. A creative study by Donnelly et al (1991) found that people who lost weight by dieting alone lost as much weight (20.4kg) as groups who supplemented their dieting with aerobic exercise, weight training or both.

Nieman et al (1998) found that a group of people who dieted without exercising had a 7.8kg weight loss, while a group who dieted while doing a walking program lost 8kg. A group of fitness walkers in the same study, who did not use any dietary intervention, lost only 1kg.

A meta-analysis of 493 exercise and dieting studies concluded that modest amounts of aerobic exercise (2–7 hours/week), plus dieting, result in a weight loss of 10.98kg over 15 weeks, while diet-only programs result in a weight loss of 10.66kg (Whatley et al, 1994; Schoeller et al, 1997; Mattson et al, 1997). Clearly the weight loss in these studies is due to the dieting, not the running or exercise.

Aprés run

What about the idea that resting metabolism is revved up after running? Do you burn as many kilojoules after you run as you do during the training effort? Here is an opportunity to put this myth where it belongs: in the rubbish bin. Well-researched studies show that the “after-running kilojoule burn” is minimal, not worth tuppence.

Jogging for 30 minutes at 19 minutes per kilometre, for example, despite causing your resting metabolic rate to stay elevated for 20–30 minutes, burns only 50 extra kilojoules (Sedlock et al, 1989; Short et al, 1997)! When running intensity is increased to 75 per cent of aerobic capacity for 35–45 minutes you burn only 60–120 kilojoules (Bahr et al, 1991). What about really long runs? You’d think they would cause a big after-running calorie burn. Studies that looked at extended running for 80 minutes or longer also found a very modest after-running kilojoule burn (Phelain et al, 1997; Withers et al, 1991).

Burn more kilojoules

The post-running “kilojoule burn” is closely related to another metabolic myth: that of the long-term revving-up of your post-exercise metabolism. If your metabolism turns over at a higher rate, theoretically you should burn more kilojoules each day.

Research on this topic is conflicting. Some studies have found that highly trained elite runners have higher resting metabolic rates (RMR) than sedentary people (Sjodin et al, 1996; Poehlman et al, 1992; Toth et al, 1995), while others have found no differences (Meijer et al, 1991; Broeder et al, 1992; Wilmore et al, 1998). Other research shows that athletes’ resting metabolism stays higher for up to 24 hours after a very long and very strenuous training bout but not 48 hours after (Schultz et al, 1991; Bullough et al, 1995). Once again, unless you are an elite runner doing 60+ miles a week with occasional long runs over 30km, and much of it at a fast pace, this is unlikely to be an issue that will affect your weight loss.

How much should you cut back your diet?

Caution is advised when cutting back kilojoules to lose weight. The more you restrict your kilojoules, the more lean mass you’ll lose and your body will cling to its fat for this “emergency” situation. The take-home message here is that you should aim to reduce your kilojoules by only 2100–4200kJ a day, rather than very low kilojoule-restricted diets that reduce your daily intake by 5040–6300kJ a day.

Running rationale

Now for the good news for runners. While running is a poor performer at weight loss, it has been shown to help maintain our goal weight once achieved. Consistent exercise and running show up as being among the top predictors for success in weight control and maintenance. Other habits for maintaining ideal weight include controlling eating habits and other behavioural techniques, measuring weight frequently and eating fewer high-fat foods.

Running also confers some marvellous health benefits. It improves cardio-respiratory endurance (aka VO2 max), improves blood lipid profile (decreases triglycerides, decreases total cholesterol, decreases your risk for hypertension, obesity, cancer, heart disease and diabetes) and, finally, not to be underestimated is the dramatic improvement in our psychological state of wellbeing with decreased anxiety and depression.

You may experience a weight gain of a couple of kilos during your first few weeks of taking up running; this is normal and reflects an increase in your lean body mass (muscle), water storage in the muscle and an increase in plasma volume. Another thing to watch for when dieting: you will eventually reach a point of diminishing returns, where your rate of weight loss slows down — this means you are approaching your ideal weight.

Running, then, is not a particularly efficient way to lose weight. It’s what you put in your mouth (or don’t) that counts far more than pounding out the miles. Nutrition and diet is by far the major player in the weight-loss game unless you’re a runner cranking out an hour or more of fast running each day. However, running gives us some spectacular health benefits and has been proven to help us maintain our weight once we have achieved our weight goal.

9 rules about running and weight loss

Rule #1

It takes long workouts (an hour or more) to burn enough kilojoules to seriously contribute to weight loss.

Rule #2

You must run (very) regularly for weight loss to take place, ie 5–7 days a week.

Rule #3

You have to work out at a high intensity to burn significant numbers of kilojoules when running. Moderate levels of running are not enough to reduce your weight.

Rule #4

The main key to successful weight loss is reducing the number of kilojoules you eat, not running.

Rule #5

The after-running “kilojoule burn” is minimal and not enough to contribute to weight loss.

Rule #6

Beginning runners on weight-loss programs are unlikely to have higher resting metabolic rates than sedentary people. Higher RMRs among elite runners are transient and appear for up to 24 hours after very long and hard training efforts.

Rule #7

Restrict your kilojoules by no more than 2100–4200 a day; avoid very low-kilojoule diets as they will cause you to retain your fat and also cause higher losses of lean mass, such as muscle.

Rule #8

Running is excellent for maintaining your weight after you have reached ideal weight, so don’t stop running.

Rule #9

Run for good health, not weight loss

References available on request

 

Roy Stevenson has a Masters degree in exercise physiology from Ohio University. He has taught exercise science and nutrition at Seattle University, University of Puget Sound, Highline Community College and Lake Washington Technical College. W: www.Roy-Stevenson.com