Is there a difference between reducing calories
evenly throughout the week (daily calorie restriction)
and fasting (extended duration calorie reduction)
in terms of fat metabolism?
University of Florida health researchers recently published a
study in the journal, Obesity, that emerging findings in
scientific literature show intermittent fasting can be a reliable
means of weight loss and may optimize physiological
functioning, enhance performance and slow the aging
and disease process.
To understand why, researchers said, one must look to how
the body essentially flips a “metabolic switch” during fasting.
This means the body moves from burning glucose, or sugar,
for energy to fatty acids and their byproduct, ketones.
During fasting, the body converts fat into fatty acids,
which can be absorbed by the blood.
Stephen Anton, Ph.D., the division chief of clinical
research for the UF College of Medicine’s department
of aging and geriatric research and the paper’s lead
author, said research indicates ketones are the preferred
fuel for the brain and body during periods of fasting and
Ketones, he said, are a cleaner source of energy than
glucose, protein or carbohydrates, the body’s other
sources of energy. Typically, he said, after eight to 12
hours of fasting, the levels of ketones in the blood
Anton’s paper looked at two popular forms of intermittent
fasting. The first is time-restricted feeding, when the
dieter eats during discrete windows during the day.
For example, they might fast 16-18 hours a day,
eating during the other six to eight hours.
In that window, the dieter isn’t restricted to what they eat.
The second approach is called alternate-day fasting.
In the more common model of this fasting regimen,
people limit their meals on one day, usually to 500 calories.
On the next day, they can eat anything at all.
A second version of this fasting method is to eat
nothing at all on one day while feasting the next.
In a review of scientific literature, Anton and his
colleagues found that people lost significant body
fat in 10 of 10 clinical trials involving alternate-day fasts.
Three of four time-restricted feeding studies
demonstrated significant fat loss.
Anton said research in rodents and other nonhuman
species points to the possibility that food restriction,
and the turning of that metabolic switch, can lengthen
lifespan, improve metabolic health, cognitive and
physical performance, lower inflammation and lead
to superior cardiovascular health.
More research needs to be done to see if there are
additional metabolic benefits that are unique to
intermittent fasting, aside from fat mobilization.
There are downsides to fasting and it is not appropriate
for everyone. Please discuss fasting with your doctor.
The concerns with intermittent fasting:
Reported risks with interrmittent fasting include nausea,
dizziness, abnormal liver function, decreased bone density,
thiamine deficiency, and poor athletic performance
on fast days.
Because food quantity and quality are unrestricted on feeding days/hours with intermittent fasting, poor food choices can
erase the benefits of fasting and harm health.
What about standard dieting (daily caloric restriction)?
Standard daily caloric restriction has been proven time
and again to also increase fat mobilization, particularly in combination with exercise.
Standard dieting encourages consumption of
nutrient dense, energy efficient foods.
If you have fat to lose, how do you proceed?
Ask yourself the following:
What can I stick with long term?
What works best for my life and my body?
What approach will facilitate making the best overall
food choices for maximal nutrition and wellbeing?
The ultimate objective is life long health and wellness
so choose lifestyle habits that you can and will maintain
and that help you reach your goals!