Men are from Mars and Women are from…

…Mars! Sorry, that one should be obvious, despite what John Gray suggested, men and women differ less physiologically than we think; Dr’s often have a poor understanding of actual research evidence. One of those myths has extended to weight loss. As the media has portrayed, it is more difficult for women to lose weight than it is for men. A cursory glance at the research sometimes supports this. However, when you dig a bit deeper, it is more complicated than that, and, as it turns out, probably not true. A new systematic review in Exercise and Sports Sciences Reviews by Caudwell et al. examines the literature on sex-based difference in weight loss and indicates that when men and women burn an equivalent number of calories, their weight, and in particular body fat loss is similar. This is a relatively short review that most people should be able to read and understand. The authors summarize their findings as such:

  1. Matching energy expenditure will likely lead to similar results
  2. You should focus on changes in fat and muscle (ie, body composition), rather than weight,
  3. Individual results may vary not due to exercise response, but due to variability in appetite; appetite differences are independent of gender.
  4. Even without loss, the benefits of exercise far outweigh any other intervention (sorry, I embellished that last part a bit because its true)!

My take This is a good paper outlining some excellent studies, as well as the flaws in interpretation of many of those studies. Reading through the paper can get a bit confusing, as the authors note there are differences between men and women in weight loss, only to go on to outline why it may not be the accurate. Some of these issues are clear study design problems, like using overweight men and normal weight women; who wouldn’t think that its easier to lose weight when you actually have extra weight to lose? Other issues lie in self-reporting of activity, which can be fraught with numerous problems, and particularly supervised vs unsupervised exercise sessions. Recent research strongly supports that evidence-based training with a qualified trainer yields far better outcomes than training alone. The last issue is controlling diet. I have seen firsthand how lack of dietary control can undo everything exercise should improve. While I am unclear on the specific research, my own experience suggests that EXERCISE IS NOT an appetite suppressant, and at best, it is likely highly variable, as this paper indicates. Regardless of whether it you’re conducting research, training a client, or trying to lose weight yourself, failing to control for diet is likely to lead to failure. Most professionals would say that at least modest caloric restriction (200-500 kcal/day) is needed to aid weight loss. More than that, and you begin to compromise training, which is not what you want. Finally, much has been made about exercise alone being ineffective for weight loss. In general, I agree across the board. However, there is one problem with this statement. For the average person, they are not exercising enough. I (and others) have generally found that 5 hrs or more exercise each week (~2000-3000 kcal) is needed to alter body composition “significantly”. Interestingly, this is the recommendation made by the ACSM for obesity exercise programs. If you or your client simply cannot or will not exercise more than 3 hrs each week, success even with caloric restriction is unlikely. Moreover, at that dose (5 hrs), the health benefits of exercise sky rocket; greater increase in HDL cholesterol/reduced triglycerides, decrease in BP, cancer reduction…I recognize that 5 hrs is a commitment, but god damn, it beats feeling like sh!t and not being able to walk up a few flights of stairs! Bottom line Men and women are likely similar in weight loss, and require similar programs to succeed. However, even without weight loss, the health benefits of exercise alone are still not fully calculable but far exceed ANY drug on the market!

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