Why Are You Still Hungry?
It's been less than two hours since your last meal. So, why are
you still hungry?
If you've ever tried to lose weight, you're probably familiar
with that intense sense of hunger, which just won't go away.
A recent study, which made front-page news here in the UK, could
have the answer you're looking for...
In August 2002, endocrinologist Stephen Bloom and colleagues at
Imperial College London found that when they injected a hormone
called peptide YY3-36 (PYY) into rodents and humans, it decreased
hunger for 12 hours or more.
Rodents on the peptide also reduced their weight gain, leading
some to herald PYY as a potential new anti-obesity drug. However,
not all groups have been able to replicate these results, leaving
the peptide's promise in the lurch.
A former member of Bloom's team, endocrinologist Rachel Batterham
of the University College London and colleagues, took another stab,
this time from a different angle.
Batterham's team first looked at what kind of food best satisfies
hunger. They studied nine obese men and 10 normal-weight men. After
brief fasts, the men ate different meals. Each of the meals (a
high-protein meal, a high-fat meal, and a high-carbohydrate meal)
had the same number of calories.
All the men said the high-protein meal best satisfied their hunger.
Interestingly, the normal-weight men found the high-fat meal
more satisfying than the high-carbohydrate meal, while the obese
men did not.
Measurements showed the high-protein meal triggered the most PYY
in all of the men. In the normal-weight men — but not the
obese men — the high-fat meal triggered more PYY than the
high-carbohydrate meal.
Batterham's team also genetically engineered a mouse strain that
did not have the PYY gene. These mice ate huge amounts of food,
and quickly became obese.
Normally, obese mice fed a high-protein diet will eat less and
lose weight. But a high-protein diet didn't help the PYY-defective
mice lose weight unless they also got PYY treatments.
"Increasing the protein content of the diet augments the
body's own PYY, helping to reduce hunger and aid weight loss," says
lead researcher Dr. Rachel Batterham.
"One potential weight loss strategy is therefore to increase
the satiating power of the diet and promote weight loss through
the addition of dietary protein — harnessing our own satiety
system," Batterham says. "Such a diet is perhaps more
typical to that of our hunter-gatherer ancestors."
However, the research is unlikely to lead to supplements containing
PYY as a weight-loss product, says Dr. Batterham.
"PYY is a protein so if it is taken in tablet form it is
broken down and doesn't pass into the blood. Thus to increase PYY
it either has to be given by another route (intravenous, subcutaneous,
transdermal, nasally) or we can try and increase the body's own
circulating levels by modulation diet," she concludes.
So, what does this mean for you?
The information that protein helps you lose weight by helping
you control your appetite is so old you'll probably catch it on
a late night re-run of Starsky and Hutch.
Yet this research actually made front-page news here in the UK,
with an article in the Daily Express describing it as "ground-breaking."
The article also expressed the usual misplaced concerns about
safety, with one expert cautioning against protein on the basis
that there have been "no long-term studies of high-protein
diets," and that high-protein diets "can cause problems
with the kidneys and make people feel lethargic."
Neither comment is based on any evidence or research that I'm
aware of. A number of long-term (12-24 months) studies of high-protein
diets (which I'm defining as one that derives around 30% of its
total calories from protein) have been completed, and none show
any indication of adverse health effects (see The
Anatomy of a Balanced Diet for more information).
The idea that protein causes "problems with the kidneys" has
been around for years, but there's little
evidence to show that protein - even at a level twice the current
RDA - has any negative effect on renal function in someone with
healthy kidneys.
About The Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you're stuck
in a rut with your current exercise and diet plan... fed up with
only losing a pound here and there... or still skinny after months
(or even years) of trying to build muscle and gain weight... click here now for instant access to his step-by-step muscle-building and fat-burning workout routines.
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Reference
Batterham, R.L., Heffron, H., Kapoor, S., Chivers, J.E., Chandarana, K., Herzog,
H., Le Roux, C.W., Thomas, E.L., Bell, J.D., & Withers, D.J. (2006).
Critical role for peptide YY in protein-mediated satiation and body-weight
regulation. Cell
Metabolism, 4, 223-233
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