What Physical Activity Can Do

I had the opportunity to attend a lecture  conducted by a scientist from the University of Pittsburgh today.  He studies the impact of physical activity/exercise on weight loss and conditions related to obesity (diabetes, inflammation, HTN, heart disease).  His name is Dr. John Jakicic and he has had numerous studies published in peer reviewed science journals.  IN fact, I recall having read some of the studies that he referenced today.

I went to the lecture to see if he would present anything to support or challenge my assertions.  In case you have forgotten my stance (which developed from reading a lot of research), it is this:
Physical activity is very important and effective in reducing disease occurrence, in preventing adverse outcomes due to a disease, in promoting successful or active aging and for managing moods - or mental health.  It assists in weight loss and weight maintenance, but is not the best strategy for weight loss on its own.  Physical activity is associated with significant weight loss only in the presence of caloric reduction or restriction.  I.e. eating less.  

Before we get into that - let me be very clear that exercise can improve health even in the absence of weight loss and even in persons who are obese.  Obese persons who exercise are healthier than obese persons who do not.  Obese persons who exercise can have some improvement in risk factors even if they do not lose weight. Let me break that down.  An obese diabetic person who only exercises may not lose weight, but research supports that exercise alone can improve their blood sugar (or hemoglobin A1C).  Exercise can moderate blood pressure numbers and reduce inflammation (CRP) that increases the risk for heart attacks.  Exercise alone is helpful. 
Exercise AND weight loss are the best treatments for obesity and overweight.

Dr. Jakicic showed that exercising more than 300 minutes a week (w/out changing the amount of food eaten) led to a 3% weight loss - or about 5 pounds. [that is equal to about ten 30 minute walks a week] He told us that we (exercise and public health professionals) needed to be careful about what we said to people regarding exercise.  We needed to make sure that people maintained realistic expectations. He gave the example of the beginning of a new year when everyone heads to the gym and works out every day but the weight does not come off because they do not also change their eating.  The people have gone to the gym because they think they just have to exercise more and the weight will come off.  When that does not work, they quit the gym.

He actually showed a great chart during his presentation.  The chart had several lines that went from left to right.  The lines represented time one (baseline) and time two and the further the line dropped at time two the more weight the person lost.  Each line represented a different condition.  1)  for just calorie reduction, 2) a line for  exercise > 300 min a week, 3) a line for exercise at ~ 150 min a week, and 4) a line for a combination.  The diet alone line and the combo line were close together (low on the graph) - the others were up high, indicating no or few pounds lost. 
Therefore, as I have said, diet alone is far more powerful than exercise alone for ONE specific thing- losing weight.  Together they are better and best, but singularly they both have a powerful impact on health in general.