Weight Loss
Hormones of appetite and satiety — How does the brain know when we’re hungry or
full?
What about willpower?
To what degree dietary discretion can be relied on to keep your weight down varies
tremendously between individuals, and even at different times for a single individual,
depending upon many circumstances.
But to a woman struggling to lose weight — and to keep it off — the notion that
willpower alone should suffice is a lonely one. When you feel hungry, you don’t
just want the crust of the willpower biscuit.
What’s important to understand is that our behavior around eating is not always
something we can or do consciously regulate. Much of it is purely physiological,
and physiology strongly interacts with psychology.
References
If you’ve ever caught yourself eating like a robot when you’re not really hungry,
or the opposite — gotten so caught up in what you were doing that you totally forgot
to eat, then suddenly realized you were ravenous — then you’ve experienced
the sometimes paradoxical effects of specialized signaling molecules in the body
known formally as “the hormones of appetite and satiety.”
The relationship between these recently identified hormones and how the gut talks
to the brain to regulate weight is currently the subject of intensive new research
— mostly on mice — with everyone digging for clues that will help people lose weight
fast and keep it off for good.
What’s more to the point, these studies are finally helping everyone recognize
that weight loss is not simply a question of mind over matter!
Hormones that signal “I’m hungry” — or “I’m full”
This is a mixed cast of characters, some pressing the “Yes, I’m hungry” button while
others pull the “No, I’m not” lever — and, curiously enough, some do both. Some
of these are well-known hormones and others are only newly discovered, but together
they’re carrying much of what governs your eating behavior. Here’s a quick overview
of this complex network.
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Ghrelin, the main “hunger hormone” identified to date, is a peptide
released by endocrine cells mostly within the stomach’s lining. It counteracts leptin
to increase metabolic efficiency and stimulate appetite. It normally indicates hunger
— “If your stomach’s growlin’, you’re making ghrelin” — but it can also be released
after a high-protein meal.
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Neuropeptide Y (NPY) is a super potent stimulator of feeding behavior,
and it’s also the most abundant neuropeptide in the brain. In addition to its function
in feeding behavior, it also takes part in circadian rhythms, sexual functioning,
and anxiety responses. Clearly an important player!
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Leptin — from leptos, the Greek word for “thin” — is synthesized
within fat cells, and works as a “satiety factor” on the hypothalamus to dampen
eating behavior while increasing energy expenditure. Leptin appears to act, at least
in part, by inhibiting NPY synthesis and release in the hypothalamus. New hopes
of a magic weight-loss pill based on leptin have never reached fruition.
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Adiponectin, a mixture of anti-inflammatory peptides secreted by
fat cells, helps regulate energy balance and the metabolism of sugars and fats,
as well as increasing insulin sensitivity. But the paradox, again, is that overweight
people often have less circulating adiponectin than slim ones, and what triggers
its release from fat cells is still unclear.
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Peptide YY (PYY) has been shown to slow digestion, suppress appetite,
and significantly reduce food consumption.
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Cholecystokinin (CCK) is released in the duodenum in response to
high-fat or high-protein meals, and signals the brain to produce a sense of fullness
or satiety — fatty meals are especially effective.
Hunger’s messages — what our other hormones have to say
It may be tempting to think of the above hormones as “niche” players with somewhat
specific effects on our desire to eat, but the reality is that we don’t fully understand
their effects, and many of our more well-known hormones also play into the equation.
When it comes to natural weight loss, the hormones that regulate metabolism play
an enormous role, with the three major hormones in the body — insulin, cortisol,
and thyroid hormones — having the most to say.
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Insulin. Any discussion about hormones, metabolism, and healthy
weight would be incomplete without including this major player in the hormone scenario.
Insulin determines whether blood sugar gets used right away for immediate energy
or stored as fat instead. And because fat is not simply a passive energy-storage
site (as previously thought), but functions an endocrine organ that produces important
hormones itself, what we eat really does matter when it comes to losing weight and
keeping it off. Insulin levels are directly affected by your diet, particularly
the ratio of carbohydrates to fiber, fat, and protein, and any disruption in the
insulin-regulating mechanism, such as insulin
resistance, has an instant effect on several of the lesser metabolic hormones.
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Thyroid hormones may also be playing a lead role in your unique
physiology. Women often ask us if a recent increase in weight could be due to a
thyroid imbalance. The thyroid does act
much like a gas pedal in regulating your metabolism, but very often we find it has
an indirect relationship to weight gain, where imbalance between other hormones
is causing sluggish thyroid function.
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Stress hormones. Adrenal imbalance caused by excess anxiety, stress
and cortisol production is typically at the top of the list when it comes to unwanted
weight related to hormonal imbalance. Sustained high cortisol levels can lead to
intense cravings and binge eating. High cortisol production can throw off any or
all of the other hormones in the body, major or minor, setting off a chain
reaction that puts your body into crisis mode. The simple significance of this is
that no diet will succeed if you are under tremendous stress — no matter what you
do. A simple saliva test can reveal whether your daily cortisol levels are in line.
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Melatonin, the hormone that regulates the circadian rhythm, also
factors into your hunger time-clock. Research shows that sleep deprivation throws
off melatonin production, which in turn influences leptin and ghrelin production.
In one study, subjects who were chronically sleep deprived had 15% more ghrelin
than those who were well-rested. There is also some evidence that lack of sleep
affects your levels of human growth hormone (hGH), because “pulses” of
hGH are released at night.
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Sex steroids — Let’s not forget estrogen, progesterone, and testosterone.
Adequate levels of estrogen seem to help in hunger regulation, simulating the soothing
“full” effect of serotonin. An imbalance in the ratio between estrogen and progesterone
triggers cravings, as anyone who is familiar with premenstrual binges can attest!
Add in the negative effects of stress hormones, and you begin to understand why
women accumulate abdominal fat during perimenopause. (See our article on
weight gain in perimenopause and menopause.) If a woman is testosterone-deficient,
which can occur with poor nutrition or during perimenopause, she will have difficulty
building muscle mass no matter how much she works out. Testosterone production relies
on adequate levels of cholesterol, the building block of all sex hormones.
Hormonal balance on every level
We are learning that many different hormones transmit or dampen hunger signals,
indirectly or directly influencing our best efforts to lose weight. But we still
have a long way to go before we fully understand how the hormones of appetite and
satiety actually work in humans.
But we do now know that there are very real hormonal factors involved — it’s not
just your genetics or your willpower or your eating habits — and that balancing
all of these elements is what it takes to balance the weight equation that so many
women are grappling with.
As we uncover new pieces to the inner workings of our metabolism, we can see clearly
how crucial hormonal balance can be to losing weight naturally and keeping it off
for good. Over the years, we have helped many women successfully balance their hormones,
safely and naturally, and in the process lose unwanted weight — and we can help
you, too.
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References & further reading on the hormones
of hunger and satiety
Last Modified Date: 05/25/2011