Is Diet Or Exercise More Important

The ultimate questions : Is Diet Or Exercise More Important ? A lot of people ask me which is more important for losing weight: Diet or Exercise? If you want the short answer is that both are vital for living a healthy lifestyle. Now if you would like the long answer check out the awesome in-depth article provided to us by Vitals - LifeHacker! Is Diet Or Exercise More Important?

Diet Versus Exercise

A Primer on Calories

At a physiological level, weight loss and weight gain revolve around caloric consumption and expenditure*. Because of this, it's important to understand the basics of calories. Put simply: we lose weight when we eat less calories than we expend. Conversely, we gain weight when we eat more calories than we expend. In order to lose one pound of fat, we must create a 3,500 calorie deficit, which can be achieved either through exercise or diet. I

*As an aside, it's worth noting that some argue that carbohydrates and insulin are the culprits behind weight loss and weight gain in what is called "the insulin hypothesis of obesity." While controlling both carbohydrates and insulin may be important for some individuals, this hypothesis has been thoroughly debunked.

Let's say that a 200 pound man wants to lose one pound in a week. Through exercise alone, he needs to run about 3.5 miles per day (or 24.5 miles total), assuming his diet stays the same. Through dieting alone, he needs to cut back 500 calories/day (the equivalent of two Starbucks Frappuccinos), given his exercise regime stays the same. Theoretically, the two should achieve the same results.

But in the world of fitness theory and reality are not the same thing, because theory does not account for adherence. We don't live in a magical house that contains a gym, a Whole Foods, and a personal staff of nutritionists and trainers. Instead, we're left about our own devices in everyday life. What happens then?

What the Research Says

Dr. John Briffa, who runs an excellent health blog, analyzed a study examining weight loss without dietary intervention here. He explains:

In this study, 320 post-menopausal women whose weight ranged from normal to obese were randomised to either an additional exercise or no additional exercise group (the control group). Those in the exercise group were instructed to take 45 minutes worth of moderate-vigorous aerobic exercise, 5 times a week for a year. Both groups (the additional exercise and the control group) were instructed not to change their diets.

At the end of the year, it was found that the exercise group, compared to the control group, lost an average of 2 kg (4.4 lbs) of fat. I'd say that quite a lot of us would be glad to drop a couple of kgs of fat. But now I'd also like to focus on what these women had to do to achieve this loss.

While the exercise group were instructed to exercise 5 times a week for 45 minutes, what they actually did was exercise for an average of 3.6 days each week. Total exercise time averaged 178.5 mins per week. We can multiply this by 52 to get the total number of minutes exercise over the course of the year, and divide this by 60 to convert it into hours. Doing this, we get a total of just under 155 hours. That's about 77 hours of exercise for each kg of fat lost.

Most people would balk at the idea of exercising for 77 hours to lose 1 kg of fat. (Or equivalently 35 hours to lose 1 pound, for us American folk.)

But what about simultaneously exercising and accounting for dietary intake?

One study, published in the International Journal of Obesity and Related Metabolic Disorders, took trained subjects and had them track dietary intake along with energy expenditure. On paper, there was an overall caloric deficit created by the subjects. However, when researchers examined empirical changes, no weight was actually lost. As it turns out, subjects were simultaneously underestimating caloric intake and overestimating caloric expenditure.

Compare the studies above to the hilarious self-experiment by a nutritionist who went on the "Twinkie Diet" and subsequently lost 27 pound in 10 weeks. (Pro tip: Don't try this at home.)

Why Exercise-Focused Regimens are Relatively Ineffective for Weight Loss

If you're perplexed by the information above, don't worry. There's a simple explanation behind it, which we'll break up into two parts s

Reason 1. Calorie expenditure through exercise is relatively small in the grand scheme of things.

In order to see why exercise-focused weight loss programs might yield low efficacy, it's important to understand the accounting behind our daily caloric expenditure.

We spend most of our calories every day just "staying alive." This is known as our "resting metabolic rate." The Katch-McArdle formula, which takes into account one's body fat percentage, is the most accurate way to calculate this number, which is equivalent to:

9.81 x your amount of non-fat mass + 370 calories per day

Let's say you are a 200 pound man who is at 30% body fat. You expend 1,743 calories per day just staying alive. (200 x (1-.30) * 9.81 + 370 calories)

He'll expend about 10% on top of that by what's known as the Thermic Effect of Food (TEF): the amount of calories that he spends digesting and absorbing his dietary intake.

Add another 10% on top of that through a metabolic process known as NEAT ( Non Exercise Adaptive Thermogenesis). This is the amount of calories wasted through things such as fidgeting. Unfortunately, this can vary greatly from individual to individual.

This means that without so much as getting out of bed, our subject has already expended 2,100 calories.

Now, add another 10% for getting out of bed and going about his daily routine and he's already burned 2,300 calories.

Adding exercise into the equation barely makes a dent in his overall caloric expenditure; most of the work is done before he puts on his running shoes. Now I am not saying that you shouldn't exercise, but rather, it's important to realize where a majority of your caloric expenditure is coming from. You wouldn't take up a paper route in order to supplement a 100k/year salary, would you?

Reason 2. People are horrible estimators of calories in vs. calories out.

Take a look at another study, this one in the Journal of Sports Medicine and Physical Fitness, in which researchers asked the subjects to exercise, estimate their caloric expenditure, and then took them to a buffet afterwards. Subjects were asked to consume the amount of food that they believed they burned in calories. (Sidenote: Where can I sign up for one of these?)

The subjects ended up eating 2-3 times the amount of calories that they burned.

The takeaway from all of this information is that calorie expenditure doesn't count for much, and human beings are generally terrible at estimating both expenditure and intake.

Hopefully you found this insightful. Obviously exercise wont save you from your "big Mac" diet but if you spend some time thinking about what you are eating and determine how many calories you nee to consume on a daily bases, exercise will have a bigger impact on weight loss.