The Role of Exercise in Weight Loss: Part 1

One of the questions I get quite often is “How much exercise should I be doing?”

Unfortunately, the answer to that question, like so many others in nutrition and fitness is: it depends.

Are you exercising to maintain health? Trying to lose weight? Wanting to gain muscle? Or are you training for high performance sport?

All of these goals require a vastly different type and amount of exercise.

For heart health, 30 minutes of moderate-intensity cardiovascular activity, three times per week goes a long way towards keeping you from spontaneously keeling over dead.

But if you think 90 minutes of weekly physical activity is all that it takes to build the body of your dreams, think again!

No matter how noble an intention it may be to exercise and eat strictly for health related reasons, the reality is that most people diet and train for aesthetics. Humans appear to have a near universal desire to look good naked.

Whether this is a product of Darwinian evolution or just plain vanity, weight loss always seems to be foremost in our minds.

Given that weight loss is everyone’s primary goal, the question du jour becomes: how much exercise is needed for weight loss.

In order to quantify an answer, we must first acknowledge exactly what exercise can and cannot do for body composition. Over the next three articles, we’ll be looking at some exercise research that will hopefully help you understand exactly what you should be doing going forward.

So without any further ado, let’s get started.

Reality Check #1

Exercise does NOT produce weight loss

Although this sounds controversial, talk to anyone who trains at a commercial gym and they’ll swear they’ve seen thousands of regular exercisers who train religiously for years, yet never seem to improve their physiques.

So what gives?

Are our gym voyeur friends merely making faulty observations or is exercise actually ineffective for producing weight loss?

While I can’t vouch for the former, the latter certainly is true.

Exercise appears to be a lot worse at producing weight loss than you’ve been led to believe, particularly if exercise is your sole weight loss strategy.

A recent study published in the in the Journal of Nutrition and Metabolism (Lockwood et al. 2008, Nutrition & Metabolism, 5:11), really hammers this point home.

In the Lockwood study, thirty-eight sedentary, overweight individuals were divided into three experimental conditions and followed for 10 weeks. The three conditions were:

  1. Control: They did nothing for 10 weeks (life as a control subject sure is rough!)
  2. Exercise group: They exercised 5x per week. Two sessions were full-body resistance training and 3 sessions consisted of aerobic exercise.
  3. Exercise + high protein supplement: Same exercise program described above, but in addition they were asked to consume 1-2 protein shakes a day.

Add everything up and over the 10 weeks, both exercise groups performed 50 training sessions!

For a sedentary individual, going from nothing to 50 training sessions over 2 ½ months is a huge jump in training volume and we’d expect to see some serious results. As a bonus, the researchers had someone supervise all the training sessions, so we know the participants actually completed the workouts in question.

So after 10 weeks, what did these researchers find?

Body Composition Changes

Control: Lost 0.4 kg of fat and gained no muscle. No real surprise there.

Exercise only: Lost 1.1 kg of fat, gained 0.3 kg of muscle.

Think about that for a second.

After 50 training sessions, all that these previously sedentary individuals had to show for their hours of sweat was a couple of measly pounds lost!

Considering that the sedentary group lost 0.4 kg of fat, then all that additional exercise only amounted to 0.7 kg of fat lost. Talk about depressing.

Those numbers really don’t place exercise in too positive of a light. In fact, it kind of paints the whole business of personal training in unflattering colours. Given what we’ve just seen, how prepared would you be to commit to 3 months of personal training at $75/hour if all your $3500 investment netted you was a couple of pounds of fat lost?

Having worked as a personal trainer for many years, I can tell you too many trainers don’t know the first thing about producing real results. However, before we label all personal trainers as frauds (let’s be honest, some of them certainly are), let me throw personal trainers a lifelife and suggest their inability to produce results isn’t entirely their fault.

Huh!?!? How can a lack of results not be your trainer’s fault?

Well, many personal trainers can’t produce results because they lack the proper background. Let me explain.

Remember that this study involved a third group, the exercise + protein intervention. When we look at what happened to that group, we see a very telling pattern start to emerge.

Exercise + protein: Lost 2.7 kg of fat, gained 0.6 kg of muscle.

Now isn’t that something?

Despite following the same, ineffective weight loss exercise program, the group with the minor nutritional intervention still experienced a significantly greater loss in body fat than both the exercise and control groups.

Now although some of you might argue that 2.3 kg over 10 weeks isn’t earth-shattering, keep in mind that:

  1. Exercise + diet was 3x more effective than exercise alone (-2.3 kg vs. -0.7 kg)
  2. The exercise program wasn’t optimized for fat loss (clearly)
  3. The subject weren’t dieting, they only added protein shakes

Obviously just randomly tossing in an extra serving of protein or two is not what I consider optimizing a meal plan for fat loss. However, this study does highlight the importance of diet as the primary determinant of weight loss.

Considering that most trainers don’t specialize in offering nutritional counseling, it’s no wonder so many of them struggle to produce weight loss in their clients.

Although this study helps explain why so many exercisers fail to change their physiques despite hours in the gym, it raises an interesting question: given the majority of body fat losses can be traced back to changes in our diet, why bother with exercise at all?

Definitely a good question and one we’ll investigate next week.

Till next time, train hard and eat clean!