Sponsored content
CONVERSATIONS with EXPERTS
seem mysterious and incomprehensible. But in my
judgment, it does not need to be. To me, it may be
as simple as this: before meals, many people get
hungry; after they eat, people are not so hungry.
To its core, that is the neurobiology of caloric
balance. The problem is that the neurobiological
forces that promote eating during fasting or
starvation are far stronger than those that
suppress eating when over-eating.
Specifically, fat weight loss contributes to
neurobiological mechanisms (such as decreased
leptin and insulin levels) that promote energy
conservation and stimulate starvation eating
behaviors—even when the patient is still overweight.
What can patients do to combat these
neurobiologic forces that promote fat weight
regain? One of the best measures to maintain
weight loss is to engage in a regular physical
exercise program. Regular physical exercise not
only burns calories, but it may enhance the effects
of leptin and may mitigate counter-regulatory
mechanisms that would otherwise promote
positive caloric balance.
Dr. Cannon: That’s interesting. I’ve heard about
the interaction of exercise with metabolic function
in the muscles—is that an emerging area as well?
Dr. Bays: Yes, it is conceivable that, in addition
to the various factors released by adipose tissue
and adipocytes, muscles could also produce
analogous factors that affect caloric balance.
What I find intriguing is all the myths regarding physical activity. One of those is in regard to
the optimal type of exercise: either dynamic or
resistance. In general, aerobic or dynamic exercises will have the greatest potential for burning
calories. However, resistance training may have
its own advantages for caloric balance and muscular and bone health.
Misconceptions arise when patients are
told, “Every pound of muscle gained burns an
additional 50 calories per day.” This implies
that if 10 pounds of muscle are gained, resting
energy expenditure would increase to 500 kcal
per day. However, this is misleading. Firstly, for
most individuals, gaining 10 pounds of muscle is
challenging. Secondly, if muscle weight increases
and total body weight decreases, then adipose
tissue and the calories required to sustain adipose
functionality most likely decrease, as well. Thus,
in this situation, the total resting metabolic rate
really doesn’t change that much. Because the
difference in resting caloric expenditure required
to sustain a pound of muscle versus a pound of fat
is not as great as people may think.
Dr. Cannon: In that vein, there have been some
recent studies looking at glycemic control as a
surrogate endpoint of metabolic profile in dia-
52
CardioSource WorldNews
betic patients. The control group participated in
aerobic exercise was compared with patients who
performed weight resistance training or both
forms of exercise. When each group exercised
the same amount, the group who participated in
a combination of exercises had better glycemic
control. For me, that means aerobic and weight
resistance training must each contribute differently to improving the metabolic profile. Is there
anything to that notion?
that, whichever different validated diet the patient
embarks on needs to be individualized based, again,
on what works for the individual patient from a
neurobiological standpoint, as well as from the
standpoint of what the patient is most likely to do.
This approach means thinking about the
anticipated effect with regard to an individual
patient’s glucose levels, lipid levels, and other
metabolic parameters. As an endocrinologist
who routinely works with F