Sunday, October 23, 2011

Exercise, Weight Loss, and Health

This may sound familiar: You see someone that you haven't seen in a few weeks/months/years.  He has lost a lot of weight and looks fantastic.  You ask how it happened.  He then credits his new trainer, running regimen, home workout DVD, or a newly-found dedication to the gym.

What was missing is the major change in diet.  His workout may be the cause that he targeted, but it's not the real cause of the change.  What it comes to fat loss, diet is the major factor and the contribution of exercise has little practical significance.  If you don't believe me, keep reading.

Exercise and Weight Loss

  1. 334 obese or overweight (according to BMI) subjects were split into four groups [1].  One group was a control group of people that did not exercise.  The other three groups did eight months of aerobic exercise for 179 minutes per week at a moderate intensity, 114 minutes per week at a borderline high intensity, or 175 minutes at a borderline high intensity.  Researchers had the subjects continue their usual eating habits.  The results: The borderline high intensity group that exercised 175 minutes per week had the highest weight loss at a whopping 1.76 lbs. (.8 kg).
  2. 25 inactive senior women were split into three groups for a nine month exercise study [2].  One was a placebo group that performed stretching and exercises with resistance bands.  The other two groups performed aerobic exercise for about 55 minutes per workout at a high intensity, or 65 minutes per workout at a moderate intensity.  All three groups did four workouts per week.  Researchers in this study also instructed the subjects to not change their diets.  The moderate intensity group was the winner in this study, dropping 1% body fat.  The other groups saw no change in percentage of body fat.  
  3. 251 obese, type 2 diabetics were part of a 22-week study [3].  The subjects were split into four groups: a control (sedentary), a resistance training group, an aerobic training group, and a group that did the full resistance and aerobic training workouts.  All groups worked out three times per week.  Diet was monitored and managed by a dietitian with the goal of keeping energy intake even with estimated expenditure. The combined and aerobics-only groups tied for the highest weight loss at 4.8 lbs (2.2 kgs) more than the sedentary control group, whereas the resistance training group lost 1.5 lbs (.7 kgs) more than the control group.  4.8 lbs may sound good to you, but if an obese person hired me to help him/her lose weight and ended up with a 4.8 lb loss in five months, I'm probably going to be fired.  
  4. A 14 week resistance training study looked at 22 obese, adolescent Latino males, half doing strength training and half serving as the control group [4].  The exercise routine was twice per week and structured in a progressive model (increasing volume and weight load over time).  Excluding a post workout dinner provided by the researchers, diet was unaltered.  The resistance training group lost 2.9 lbs (1.3 kgs) and the control group lost about .5 lbs (.2 kgs).   

Exercise, Weight Loss, and Health

If you simply looked at the information I presented so far, you might see the aforementioned studies as failures - these obese, overweight, or sedentary people who participated in exercise programs lasting several months saw little to no change in their weight.  However, these programs were far from being failures.  The subjects experienced significant improvements in health:

  1. In the study of 334 subjects, a few of the groups experienced improvements in HDLs, triglycerides, and both systolic and diastolic blood pressure [1].
  2. The study of senior women led to a noticeable increase of insulin sensitivity in the high intensity group [2].  Even the placebo group that did resistance band exercises saw improvement in the form of decreased blood glucose.
  3. The study which featured 251 obese, type 2 diabetics led to improvements in HbA1c (blood sugar) for all three groups, and the resistance training-only group also gained 1.7 lbs. of lean mass (.8 kgs) [3].
  4. 10 out of 11 resistance training subjects in the obese, adolescent male study experienced an increase in insulin sensitivity (which will decrease the chances of developing type 2 diabetes in the future) [4].  They also gained about 8 lbs (3.7 kgs) of lean mass. 
In Conclusion...

Enough with the studies! Here are the take home messages:

  • Exercise is not a significant contributor to weight loss.  A resistance training program can limit or prevent the loss of lean tissue during weight loss [5], but the actual weight loss needs to come from diet changes. 
  • Exercise is an effective tool for improving health in a wide variety of ways.  If you don't want to adopt a healthier diet, exercise will still improve your life. 
  • Weight and health can change independent of each other.  A person is not unhealthy because he or she is overfat.  Also, improving your health does not mean that your weight has to change.

1 comment:

Jacquelyn said...

This was such an encouraging post. If I do one or the other I win. Somehow this makes it easier to see myself as successful and encourages me to do more. I miss having you as my trainer at the gym.