1. Recent Study Reveals Women Burn More Fat Than Men
A recent fat loss study published in the Journal of Applied Physiology
(2005) has shown that women burn more fat than men during
exercise.
The researchers studied the effects of an incremental treadmill test to
fatigue on 300 male and female subjects of varying fitness levels. They
wanted to determine whether the ability to burn fat was influenced by
gender, training status, fat free mass (lean body mass), and most
importantly exercise intensity.
It has been well established that the most important determinant
of fat burning during exercise is in fact exercise intensity,
whereby fatty acids comprise roughly 55% of total energy expenditure
at low intensities but diminish as exercise intensity increases.
Conversely, as exercise intensity increases so too does the
contribution of carbohydrates to total energy expenditure.
The shifting of fat and carbohydrate
contribution to energy expenditure is known as the “crossover
effect” and occurs anywhere from 50-75% of maximum heart rate
depending on gender, training status, and the study cited. This is the
point (or intensity) at which carbohydrates take over as the
predominant fuel source for exercise.
This graph shows the crossover effect from the current study.
2. The present study found several interesting findings that have also
been confirmed by numerous other studies. Some of these findings
include:
1. Relative to lean body mass, women burn more fat than men
at all exercise intensities.
There are many mechanisms thought to be
involved in the fat oxidation difference between men and women;
briefly, these include levels of circulating hormones and
catecholamines (adrenaline), muscle fiber type proportion, adrenergic
regulation of fatty acid mobilization, and activity of the fat burning
enzyme hormone-sensitive lipase.
This graph shows the contribution of fat (grey) and carbohydrates
(black) at different exercise intensities for men and women in this
study.
2. Fat is a greater contributor to total energy expenditure at
lower exercise intensities.
This goes back to the “crossover effect” that was mentioned above.
However, there are several mechanisms that inhibit fat burning at
higher sustained intensities including lactic acid accumulation and an
increasingly acidic cellular environment.
3. 3. Fitter individuals burn more fat
Both VO2 max (maximum aerobic capacity) and training status are
significant predictors of fat oxidation. This would imply that VO2 max
and training status can increase fat oxidation by increasing fat free
mass and also by increasing the capacity of the muscle to burn fat.
It also has been firmly established in training studies that trained
individuals utilize more fat at the same relative (higher absolute)
exercise intensity than untrained individuals. Training has also been
shown to be an effective means of increasing fat oxidation during
exercise in obese men and women and that the intensity found to
induce these changes was low (40% VO2 max – roughly 50% of max
heart rate).
Take Home Message
Based on these findings it is clear that the fitter you are the better
your chances of burning fat. As your body adapts to endurance
training it becomes better at saving important carbohydrate reserves
and instead utilizes unneeded fat. Therefore, get active on a daily
basis to allow your body to become a fat burning machine.
The second piece of advice I’d like to give is to you is this… WALK
EVERY SINGLE DAY!
Why?
Well, as this studies (and tons of other studies have shown) low
intensity exercise uses fat as a major source of fuel. Therefore, at a
minimum you need to make walking (a relatively low intensity activity)
a fundamental aerobic activity in your daily life. At least 30 minutes
4. per day should do the trick. Take your dog for a walk, walk with your
loved one, walk to work or home or to the grocery store – just do it!
Yuri
Reference:
Venables, M. et al. (2005). Determinants of fat oxidation during
exercise in healthy men and women: a cross-sectional study. J Appl
Physiol 98: 160 –167, 2005.
