I can imagine that 2 decades of working in the health and fitness industry would probably convince most of the absolute benefits of exercise for the human body. It would be fair to say that after observing others for many years, supporting personal training clients and engaging in regular exercise myself for nearly 3 decades, I am convinced of the great benefits that being active can do for the human body. However, it is also clear that exercise is not the cure all panacea that perhaps it is sometimes portrayed to be.
Perhaps the biggest elephant in the gym is weight loss! Exercise is promoted as the answer to weight loss in almost every magazine, blog and exercise video. It is even a major arm of the government strategy to overcome obesity and the nation’s ballooning waistlines. It seems that no matter what, exercise gets all the glory when it comes to weight loss. There is plenty of debate over diet and other factors in terms of how they impact weight loss, so why does exercise barely even get questioned? One of the aspects of weight loss that muddies the waters is that most people do not apply a single change when they try to lose weight and lower their body fat. Usually actual weight loss results from a combination of different changes to an individual’s daily practices. There are so many different strategies that could be applied alongside exercise to achieve weight loss such as low calorie diet, low fat diet, low carbohydrate diet, high protein diet, reduced sugar, less junk food, improved sleep, reductions in stress, detoxification protocols, increased activities of daily living, weight loss supplementation, diet groups, alcohol reduction etc. etc. It is rare that exercise alone with no other change is the strategy of choice. Perhaps that is a good thing too!
If you put aside all other ways to lose weight and focus upon exercise alone as the sole strategy to reducing body weight it comes across a bit lack lustre. Don’t get me wrong it does have a positive effect, but the effect is fairly small! Certainly, nothing like we tend to believe. Back in 2006 an independent group of scientists representing the renowned Cochrane Collaboration published a meta-analysis (Shaw 2006) that looked at this very issue…how effective is exercise for managing overweight and obesity. The research reviewed studies that only utilised the gold scientific standard of randomised controlled trials (RCT) looking at weight loss periods between 3 to 12 months in duration and compared different methods of achieving weight loss. Here are the facts which summarise all scientific findings on the matter up to 2005:
- General exercise as a lone strategy provided weight loss between 0.5 – 4.0 kg
- Low intensity exercise as a lone strategy provided weight loss between 0.0 – 6.3 kg
- High intensity exercise as a lone strategy provided weight loss between 1.3 – 8.9 kg
- Diet as a lone strategy provided weight loss between 2.8 – 13.6 kg
- Diet combined with exercise provided weight loss between 3.4 – 17.4 kg
- Diet combined with high intensity exercise provided weight loss between 6.4 – 19.6 kg
Out of the 6 different strategy options looked at above, it is clear that a general exercise programme is the least effective of all the methods applied. High intensity exercise as a lone strategy does improve things and appears to be about twice as effective as general exercise. However, all three lone exercise strategies fall well short of lone dietary or combined exercise and dietary strategies. The authors of this study provided some very good summary statements which help to bring in other considerations than just the factual weight loss ranges shown above.
These findings are consistent with previous reviews (Miller 1997; McTigue 2003; Douketis 2005) that demonstrate only modest (less than five kg) weight loss with exercise alone as a weight loss intervention, and improved weight loss with diet and exercise compared with exercise alone.
The results of this study support the hypothesis that vigorous activity is more effective than moderate or light intensity exercise in stimulating weight loss…However, high intensity exercise was only significantly better than low intensity exercise at inducing weight loss when undertaken without dietary change. When diet was also modified, exercise intensity did not significantly increase the degree of weight loss.
Both low calorie and low fat diets were used as comparison dietary interventions across clinical trials. Both were more effective at facilitating weight loss than exercise alone. This is consistent with the findings of other studies that also demonstrate dietary modification is superior to exercise in obtaining weight loss in overweight and obese adults (Curioni 2005; Hansen 2005).
Before you start to think that exercise is a waste of space and that you should just get yourself on a diet to lose weight, there are other benefits that should not be overlooked in relation to applying exercise as part of a weight loss strategy. These ‘additional’ benefits certainly warrant the inclusion of exercise in the battle of the bulge. The study authors state:
Positive effects on CVD risk factors were demonstrated with exercise interventions in overweight and obese adults in this study. Those who participated in exercise interventions alone reduced systolic and diastolic blood pressure, cholesterol, triglycerides and fasting serum glucose. They also increased HDL levels. The changes that were statistically significant compared with no treatment were changes in diastolic blood pressure, triglycerides, HDL and glucose… These changes were independent of significant weight loss. Weight loss does not appear to uniformly improve cardiovascular risk factors, particularly if 5% or less body weight reduction (Douketis 2005).
In short, exercise imparts considerable benefits to the cardiovascular system that help reduce heart disease and diabetes risk, even in the face of minimal weight loss. So the real take home messages of this weight loss science blog are:
- Weight loss is best achieved through a combination of dietary modification and higher intensity exercise
- Exercise is extremely effective at reducing heart disease and metabolic health risk factors regardless of weight loss