Why exercise indeed? Did you know that 20,400,000, people, on average, around the world ask this question each month? God Google tells us so and, given that he is the one counting, it would be a tad brave to argue with him. It is a great question and I’m pleased to see it being asked because when it comes to weight loss some highly problematic assumptions are often made.

Many people with a weight problem assume that we exercise to lose weight, but few realise just how ineffective it is in causing weight loss. Fewer again appreciate how the misunderstanding contributes to the 80%+ weight loss plan failure and subsequent weight regain.

So often I hear people lament, “I need to lose weight,” and in their next breath they talk about their plan to get back into exercise in one form or another. Almost as often, I will hear no mention of changing their dietary intake, no matter how hard I listen! The reason for this has become clear to me over the years – we humans are deeply emotionally attached to the food that makes us fat and we are eternally hopeful that we can lose weight without threatening our loving relationship to food.

Since 1999 the researchers in the know have realised that exercise was not an effective way to lose weight (I will come back to this development in a moment). It was a highly counter-intuitive finding that confirmed eight earlier studies dating back to 1983. Despite repeated replication studies since 1999, I suspect the majority of health professionals today are still not up to date with the research and propagate the myth that exercise is an effective weight loss strategy.

In the March edition of Choice magazine here in Australia, their “expert” doctor (because his mistake is such a common one, I won’t name him) said it was “absurd” that some weight loss clinics were telling people that exercise was not an effective way to lose weight. He then went on to proclaim the seemingly logical argument that the uninformed have used for years: “body weight is a balance of energy in and energy out” and “if we burn more energy through exercise than we take in, the body uses the fat to meet the energy requirements.”

This would be true if we were mindless robots, but add in the human mind looking for every excuse to overeat and the equation changes dramatically. I reviewed these psychological processes in detail in Weight Loss for Food Lovers when it was published back in 2006. In 2009 Time magazine reviewed the research and made it their cover story: The Myth About Exercise. The article was entitled, Why Exercise Won’t Make You Thin.

There is a simple reason why this fact went unnoticed for so long –  most studies combined exercise and diet such that it was impossible to calculate what has come to be known as the relative contribution of exercise to weight loss. Well-designed, long-term relative contribution studies are relatively rare.

Most recently, in 2011, a well-researched paper was published in The American Journal of Medicine by Thorogood et al, reviewing the relative contribution field. What did they find from studies of people exercising to a level that we know most people cannot maintain for a year i.e. 45 minutes four days a week? The average weight lost over a twelve month period was only 1.7kg – waist circumference losses were equally modest at 1.95cm. This modest result is actually better than in many studies – especially those just involving women.

It was back in 1999 when the American National Heart, Lung, and Blood Institute, in combination with the National Institute of Diabetes and Digestive and Kidney Disease, convened an Expert Panel on the Identification, Evaluation and Treatment of Overweight and Obesity in Adults (Published by Wing RR, Medicine & Science in Sports & Exercise, 1999). Only two of thirteen studies found significant differences in weight loss resulting from exercise alone.

To be clear on that point, eleven of the thirteen studies failed to find significant weight loss from the addition of exercise to dietary management!

The weight loss attributable to exercise was gender related as men lost around 2kg and women less than 1kg. The key point here is the time period – one year! Most people on a healthy, intake-focussed weight loss plan can lose 1-2kg in one month. While the relative contribution of dietary management to weight loss is closer to ten-fold, to be conservative, we can safely tell our patients that there is at least a five-fold greater benefit from putting one’s (typically limited) motivation into managing our energy intake. This is the critical psychological issue.

Why Exercise – Women listen up!

The final issue is the gender factor. A consistent finding is that the small weight loss benefit of exercise is essentially only relevant to males. In 2003, Donnelly et al published a study in the highly respected Archives of Internal Medicine. This study was particularly notable because it was intense and ran for a longer duration than most – 45min/day, 5days/week over 16 months – and most importantly of all, the exercise was supervised in a laboratory. Men lost 5.2kg on average while women (here’s the kicker) gained 0.6kg. Yes, they were obviously fitter and the weight gain was muscle, but over 16 months they only lost 200g of body fat giving a reduction in body fat percentage of only 0.8%.

I have never met a female patient who was prepared to exercise for three-quarters of an hour five days a week for over a year to lose 200g (7 ounces) of fat. On the other hand I have many patients who exercise regularly for the cardiovascular and stress management benefits of exercise. Recent research is showing that exercise stimulates BDNF – Brain-derived neurotrophic factor – a hot new player on the scene. BDNF promotes neurone repair and growth, thereby promoting creativity and laying down of memories.

Exercise, ‘motivational fatigue’ & failure experiences

There are two psychological problems with prescribing exercise at the same times as dietary change and they both increase the likelihood of failure: First, there is an increase in what is known as “motivational fatigue” as limited motivational energy is put into a strategy that after three or four months is likely to show negligible weight loss – particularly in women.

The second problem is faulty generalisation from what does not work to discard what does work. This goes to the heart of understanding the psychology of weight management. This is a major issue for people who believe that exercise should be the most important part of their weight loss strategy. As they fail to see results, motivation dies and their program is abandoned. Sadly, the misunderstanding around exercise has set up another damaging failure experience. Because of the perpetuation of the confusion around the role of exercise in weight loss, almost no one abandons the exercise part of the program while keeping the dietary component – the baby leaves the building with the proverbial bathwater.

There is an association between weight loss maintenance and exercise (although probably not causal). With this in mind, along with the issue of motivational fatigue, I recommend patients change their eating lifestyle in a sustainable way first. During this phase I encourage them just to move more e.g. take the stairs, park further away and walk etc. Once the new eating lifestyle is in place, then we move to developing a regular exercise regime to get all the benefits that regular exercise offers.

So, why exercise? Exercise for the physical and psychological benefits which are legion. To lose weight the primary focus must be on energy intake. Once a new healthy eating lifestyle is in place, work on developing the habit of regular exercise – for its own reasons. To pursue them at the same time demonstrates a misunderstanding of the psychological and physiological science of weight management and how motivation works.

For those interested in reading the Time article – here it is: Why Exercise Won’t Make You Thin, August 2009 it is worth the read.