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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?

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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.

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I agree, a combo makes the diet easier and you'll burn off additional calories. – Ivo Flipse Jun 14 '11 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 '11 at 9:16
+1 million for advocating weights and not starving yourself! – Mike S Oct 17 '12 at 22:47

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.

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Thanks. Do you have any links to provide references? – TrojanName Jun 15 '11 at 9:17
The references can be found in this book:… – Ryan Miller Jun 15 '11 at 12:23

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.

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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 '12 at 22:52

Exercise is by far more effective than dieting. Dieting slows metabolism while exercise speeds it up. I run 8-10 miles a day and burn about 700-900 calories a day, I have to eat almost 3000 calories a day just to maintain my weight. I tried dieting and had no success.

Started running religiously and dropped 70 pounds. I now eat whatever I want and have actually lost 10 more pounds. As long as you burn enough, you don't have to diet. why do you think many triathletes and marathoners eat a crap ton of bagels, huge bowls of pasta, or lots of donuts and are skinny; EXERCISE trumps dieting, but nutritionists hate us runners and say what we are doing is unhealthy.

I had one so called "dietician" blast what I did and said marathon running was bad for my health. They do this because they know that exercise is a successful way of losing weight without starving yourself. Many of these Hollywood nutritionists endorse crash diets - 1200 calorie diets - and are scared to death that the fitness community will drive them out of business because you see athletes eating 3000+ calories a day, eating pasta and donuts and keeping the weight off. People it's simple: calories in vs calories out, if you burn 1000 calories a day and your requirement is 2000 calories, you are going to lose 2 pounds a week by just eating your requirement, lose 1 pound by eating 500 above. Exercise is key

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This answer could have been better without insulting and just a report of personal experience. – Baarn Oct 17 '12 at 13:56
This is not an answer. This is opinion and ranting. -1 and flagged. – JohnP Oct 17 '12 at 14:19
-1 @EAO Do you really think running 10 miles a day is for everyone?! I've never run more than 3 miles in one go in my life and to be honest I don't want to. Its boring, joint sheering, & muscle catabolising. Whats easier - to do a little less of something (eating) or to do a thousand times more of something (exercise)? I think we know the answer to that question. – Mike S Oct 17 '12 at 22:58
Changing what you eat will also have an impact. You can't just completely rule that out. – Matt Chan Oct 18 '12 at 2:41

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