I recently read Lyle MDonald's article here about the relaitve merits of exercise versus dieting for fat loss. He makes the argument (with numbers to back up his case) that in terms of calories lost, exercise will achieve far less than a disciplined diet will. This actually makes sense to me on a gut level (pardon the pun) as over the years I never felt exercise made as much an impact on my fat levels as dieting did. So it's good to read a more formalised argument for the case. My question is: does he have facts right?


5 Answers 5


If you compare the number of calories you can burn per hour exercising to the calories you can consume per hour eating, eating definitely wins out. It's so easy to "undo" the weight-loss benefits of exercise. Even running pretty hard for half an hour, I probably only burn 300-400 Calories (table estimating Caloric expenditure), but I could go home and eat all those Calories back in a matter of minutes (e.g. .5 to .75 cups of trail mix or 2 glasses of orange juice or 1-3 slices of pizza). And running is one of the higher Calorie-burners!

That said, certain types of exercise, such as weight training, raise your metabolism so you burn more calories while you're sitting around doing nothing (more info in another answer). To me, that's a big plus. Drastically decreasing food intake, on the other hand, may actually lower metabolic rate (more info on Livestrong).

People generally have more success when they combine diet and exercise to lose weight (Source). I like doing a combination of both because if you only change your diet, or to only change your exercise regimen, you to have to go really hardcore to get results. If you do a combination of both you can go a little easier on each, which makes it more achievable.

  • I agree, a combo makes the diet easier and you'll burn off additional calories.
    – Ivo Flipse
    Jun 14, 2011 at 21:05
  • Thanks for the Livestrong link. It's important to me to see actual numbers. Also it's not so much about how many calories you can eat in an hour (I can eat a LOT!), but in fact the opposite: if your daily calorie intake goes from say 2000 down to 1000 as part of a short term diet, I don't think any exercise can match that kind of calorie "burn" in one day (even more so if sustained for 10 days or more). So in fact, in terms of effectiveness I'm tempted to think "focus on the diet, the exercise can come later for maintenance".
    – TrojanName
    Jun 15, 2011 at 9:16

If you think of "diet" in terms of "eating less" or "reducing calories", this is a bad idea. It does not work, and you lose at least as much muscle (rather more) as fat, and as little as it works, it does not work for a long time at all before you grow tired of it. In the end, you'll have more weight and less muscle, which is an unfavorable combination.

If you think of "diet" in terms of "eating correctly" or maybe "eating with some restrictions", then it can be very effective up to a certain point.

I have gone from 115kg to 104kg over one year by following the Montignac diet, without ever being hungry or feeling agonized. (It's a low carb diet, though less fanatic than some others). It takes a bit of discipline to begin with, but after a while you don't even feel like you're missing something any more. Quality of life is very good. "No beer" is the only thing that really hurts, but hey, a glass of wine for dinner is allowed.

104kg was the end of the road as far diet went, no more change. Going on the elliptic trainer for 2 hours every other day got me down to 95kg in 8 months, for a total of 20kg in 20 months (prepare to spend some money on new trousers!).

Now... going on the elliptical trainer every two days, again, is something that admittedly takes a lot of discipline, but it's entirely possible, and it works. And, you eventually get used to it, too.
Start gently if your're not in shape (30-40 mins), and add 5 minutes every day until you're at 2 hours. Never train too hard (130-140 bpm is good), and read a book or watch a DVD to make it less boring. Be sure to aim for at least 1 hour (better 2 hours) per session, because anything less than an hour is useless for burning fat.

  • Weight training leaves you with a more favourable body composition without joint wearing, muscle eating, boring cardio. If I was fat and someone told me I had to do 2 hours of cardio every day - I most likely would never do it! +1 million though for the dedication and weight loss though!!
    – Mike S
    Oct 17, 2012 at 22:52

I've given you a lot of information suggesting that exercise, as the sole means of creating weight loss, is relatively inefficient or even counterproductive. Here are the steps that you should take to best ensure your success.

  1. Determine how many calories you expend every single day. You can use ExRx's calculator here. For best accuracy, calculate this by body fat percentage. If you don't know your current body fat percentage you can use this helpful article by Leigh Peele.

  2. Reduce your calorie intake by 20% of your maintenance calories. Any time you decrease your caloric intake, it's helpful to simultaneously increase your amount of protein in order to stay satiated. (Protein also has the higher Thermic Effect of Food out of any macronutrient, meaning your body needs to expend more energy to digest it in comparison to carbs or fats.)

How much protein should you be eating on a caloric deficit? Nutritionist Alan Aragon recommends figuring out your target body weight and getting that amount in grams. For example, if you are a 200 pound woman who wants to get down to 120 pounds, consume at least 120g of protein per day.

  1. Once you are comfortable with counting calories, consider switching to counting macronutrients instead. Focusing on macronutrients, rather than calories calories, is a nice "hack" to disrupt the fact that people (myself included) are often translating exercise and eating into the same currency: calories. You can learn all about the basics of how to count macros here.

You'll notice that the weight loss recommendation above makes no mention of exercise. But while you shouldn't be factoring exercise into your caloric expenditure or intake, you should still be incorporating it as much as possible practical.


I believe he is quite spot on. Correct nutrition is just as important if not more important for weight loss and fat loss. Exercise can certainly amplify results and shrink timelines, but if you were to pick one, I'd go with eating well.

I think a lighter is a good analogy. In order to make a flame, you need fuel (correct nutrition) and a spark (exercise). While the spark is the catalyst to the flame, without fuel you'll get no flame.

  • Thanks. Do you have any links to provide references?
    – TrojanName
    Jun 15, 2011 at 9:17
  • The references can be found in this book: amazon.com/Body-Life-Mental-Physical-Strength/dp/0060193395/… Jun 15, 2011 at 12:23
  • Tell that to every sub 105kg olympic weightlifter ever. You NEED both. One is not more important than the other. Most of them don't watch their diet and some even eat like trash and still have single digit body fat in their respective weight classes. You can and most athletes do out-eat their diets. It's not optimal or efficient but picking one or the other or saying one is more important than the other is ignorant. It's comparing apples to oranges. One is the modulation of caloric intake, the other is use of available resources. How can you compare the two?
    – TfwBear
    Apr 19, 2018 at 15:03

Diet definitely. Exercise is almost a band-aid solution for weight loss, "you can't outrun a bad diet". Vox did an interesting video on this:


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