1. Exercise reduces levels of depression. There have been a lot of studies that show that when someone who is depressed begins a regular exercise regimen, their depression lessens. The major problem with these studies is that they often do not include a control group, and that those depressed patients who choose to follow an exercise regimen are possibly at the point where they were about to move out of depression anyways and that those who choose not to are not.
After reviewing the available research, I conclude that longitudinal studies show that those who participate in regular aerobic exercise (defined as 3 periods per week of exercise in which the heart rate is elevated to at least 60% of one's maximum heart rate for at least 30 minutes) are less likely to suffer from depression, anxiety, or the effects of stress. This is not quite the same as saying that exercise cures those who are already depressed. I certainly don't think it can hurt though!
2. Exercise causes weight loss. Everyone knows that exercise leads to weight loss, right? Burn more calories than you have been, and you are bound to lose weight! The truth is that it is not quite so simple. Our bodies are complicated, and many variables are involved in how our metabolism works and how we digest and use our food. The real stickler is that exercise makes you hungry! The results of several studies the have been published in the last couple of years have shown that not only is there no correlation between exercise and weight loss, people who exercise more consistently eat more also.
Before writing this article, I was aware of some of this research from Diana's diabetes training, but I have gone and read a lot more today, and the results of these studies are shocking! In one study, approximately 500 overweight women were randomly assigned to four groups. Three of the groups worked out with a personal trainer for varying times each week. The fourth group was a control group. All of the groups filled out food diaries (although they were not told to change their eating patterns) and had their weights regularly monitored. The study lasted 6 months. All four groups lost some weight, but there was no significant difference between the groups. Basically you could say that simply filling out the food diaries and having weights monitored were the causes of the weight loss. Those in the various exercise groups ate more than the non-exercisers and those exercising less.
In another study, children who went to three different elementary schools with different intensities of physical education programs wore a special monitor for one month showing their overall activity levels. They wore the monitor during all of their waking hours. This study lasted a month. At the end of the month, it was found that the actual activity levels of all of the students were the same. Although those students with a longer and more intense physical education program were more active during the school day, they were far less likely to be active in the after school hours, than those students with less physical activity during the day. It seems that not only does an organized exercise program make us more hungry, we are also less likely to be normally active at other times to make up for it!
Those were just the tip of the iceberg. It surprises me that we don't hear more about this in the media. Now, how do I feel? It does seem that people who are normally active people are more likely to lose weight than those who tend more towards sedentary activities. So although you don't need a hard and vigorous exercise program to lose weight, it is a good idea to choose active play on occasion over sedentary play.
3. Exercise helps maintain an ideal weight. Although exercise may not help you lose weight, several longitudinal studies show that those who are the best at maintaining a weight loss are those who exercise for at least 60 minutes everyday. Note that this exercise did not seem to need to be aerobic nor did it need to involve weight training. Simply brisk walking was good enough. This correlation is a good enough reason for me to recommend that everyone try to be active for at least one hour a day.
4. Exercise reduces the risk of heart disease. Another thing that everyone knows is that exercise reduces your risk of heart disease. The most common recommendation is to perform aerobic exercise for a minimum of 30 minutes at a time at least five times a week. This recommendation is supported by research. Note that there needs to be aerobic intensity for the actual cardiovascular benefit to occur. Those who exercise longer and harder up to 90 minutes a day, 6 days a week have even more improvement in their cardiovascular health, and adding 30 minutes a week of strength training decreases the risk of heart disease even more.
My feeling are that for the general population 90 minutes devoted to cardiovascular exercise most days is an unrealistic goal and could even lead to an overall decreased quality of life. I do think that regular aerobic exercise at least five times a week for at least 30 minutes is a good idea especially if you have other risk factors for heart disease.
There are other purported benefits to exercise such as increased energy levels, better sleep, and an improved sex life, but I think that I covered the main four above. As you can see, advice can be conflicting, and it can be difficult to know what is the right path to take. I really think each individual needs to assess their own situation and think about what is best for them. Be aware of yourself, and how you respond to exercise. Choose activity over inactivity, but before choosing a more formal program, weigh the pros and cons allowing yourself to make the decision that is best for you!