Energy Metabolism
Obesity has increased dramatically over the last 60 years without a
change in human genetic makeup and with a decrease in the total amount
of fat and energy consumed. What's the problem? Certainly, the
incidence of obesity can be easily related to markers of physical
inactivity (number of hours of television viewing, number of cars per
household). However, one of the central unanswered questions of obesity
is: why are sedentary individuals out of energy balance? Why is it so
difficult to maintain energy balance on a North American Diet?
 Current
nutrition policies the world over have centered on reducing the
amount of fat in diets as well as reducing the total amount of food
consumed. If Canadian trends are similar to those published in the
United Kingdom, these recommendations have had a significant effect
on reducing the total fat intake (to about 55% of that in 1980)
and energy intake (to about 88% of that in 1980). The percentage
of the total diet that is attributable to fat also declined (from
43% to 41% on average) and the fibre intake has also risen (from
9 to 12%). These changes have certainly reduced the risk factors
for cardiovascular disease, diabetes and some forms of cancer. These
reductions were the direct result of Nutrition Recommendations provided
by organizations such as Health Canada and strengthened by research
activities. However, these changes were also aimed at reducing the
prevalence of obesity - this has clearly not happened. This means
that further research into the problem of obesity is required to
discover the link between diet, genetics and physical activity.
The Energy Metabolism lab is interested in determining how energy is
stored and utilized. In particular, the relationship between dietary
fat, dietary carbohydrate and de novo fat synthesis has been directly
studied. Coupled with research on humans, these results show that, from
an energy standpoint, there are small but significant differences in
energy utilization by humans depending on the amount of fat in the diet.
However, these differences do not appear to be significant enough to
cause obesity: obesity remains a problem of too much energy in for not
enough energy out. The Energy Metabolism lab plans to carry out
continuing research into the problem of energy balance. This research
will help isolate the problems of overeating in humans and will mesh
with human research on overeating and caloric density.
The research is used in many areas of the Food Program such as policy
and standard setting. For example, the correct measurement and reporting
of energy values is important to consumers and to researchers alike
(they are used for labelling food). Some of these compounds have complex
digestion profiles making it difficult to assign energy values. In
addition, recommendations for energy consumption in the Health
Canada's Food Guide to Healthy Eating are an important activity of
the energy lab. All these activities help to ensure a safe and
nutritious food supply.
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