How Hunger Hormones Work
How Hunger Hormones Work

Hunger hormones can make weight loss harder, defeating willpower and tempting you to give up trying to lose weight. Here's how they work and what you can do about it.

How Hunger Hormones Work

By wlr Contributor Dr Muhamad Usman MD

Imbalance of “hunger hormones” can make weight loss harder. That is because hunger can often defeat your willpower and tempt you to give up on your efforts to lose weight.

We have learned a lot about these hormones in the last decade. Knowing how to manipulate them can be a cornerstone in your weight loss success.

The Top 4 Hunger Hormones

Your body has a hard time fighting hunger.

It only needs to release a few hormones to stimulate your appetite. But, it has to release more than one dozen hormones to keep it down (1).

Researchers have identified tens of hunger hormones in the last decade. But, this article will discuss the top 4 hormonal regulators of your appetite.

  1. Leptin
  2. Ghrelin
  3. Pancreatic Peptide Family
  4. Cortisol

We’ll also have a look at what can throw these hormones off balance and what you can do to minimize the risk of that happening.

How these hormones affect appetite

In a nutshell:

  • Leptin is the major appetite suppressing hormone. Increased body weight makes you resistant to its effects.
  • Ghrelin stimulates appetite. Although its levels fall during obesity, it still makes you eat more due to leptin resistance.
  • PYY and NPY are two potent peptides with opposite actions i.e. PYY suppresses and NPY stimulates appetite.
  • Cortisol makes you eat more and you make poor eating choices under stress.

See below for more detailed information on how these hormones work and interact with each other

Triggers for Hormonal Imbalance

Here are some factors that can throw these hormones off balance. Also let’s see what you can do to counter these triggers.

Trigger # 1: Crash Dieting/Fasting

This is the strongest trigger of all that can throw your hormones off balance. Your diet has a lot of influence on the levels of your hormones. A major reason why ‘crash dieting’ tends not to work is because it throws these hormones out of balance.

In one piece of research, scientists studied the effects of crash dieting on eating patterns and hunger hormones.

Although the participants lost weight, very low calorie dieting reduced their leptin (appetite suppressing) levels by as much as 40%.

Not only had they lost leptin, their bodies also developed increased resistance to leptin. Their ghrelin (appetite stimulating) levels also increased (28).

This means, you are more likely to come back to your old eating patterns and gain weight again after the diet. This is the so-called “yo-yo effect”.

You have to be a bit more meticulous, and patient, when choosing a diet. To make your weight loss plan a success, you need to eat a healthy and well-balanced diet rather than an almost starvation plan.

Research shows that leptin levels fall at both extremes of caloric intake i.e. high calorie diet and very low calorie dieting. The key here is to find the right balance.

Recommendations for Weight Loss

  • Adjust your calorie intake to the level of your physical activity and weight loss goals. It is a good idea to start off by restricting your daily caloric intake to 1200-1500 calories/day.
  • Most of your calories should come from complex carbs, proteins and unsaturated fats.
  • The formula for weight loss goes something like this:
    Weight loss = Calorie intake – (Basal Metabolic Rate (BMR)* + Calories you burn through exercise).
    *Your BMR is the total number of calories you burn without exercising.

Trigger # 2: Sleep Deprivation

Researchers have now started to unfold the mysteries behind sleep. No aspect of your physical or emotional being remains untouched by sleep and your weight is no different.

When it comes to weight, sleep has profound effects on your hunger hormones.

Here is what research says sleep deprivation does to your hormones (29-33).

Hormone Effects of Sleep Deprivation
Leptin Less than 8 hours sleep can cause 16% reduction in leptin levels.
Ghrelin Ghrelin levels can increase by 32% with a single day of getting less than 7 hours of sleep.
Cortisol A single day of sleep deprivation can increase cortisol levels by 37%.
NPY Results of studies done on mice show that sleep deprivation causes greater food intake and higher NPY levels.

Sleep deprivation causes an increase in appetite promoting, and a decrease in appetite suppressing, hormones.

Here is what you can do:

  • Get at least 7-8 hours of sleep daily.
  • The quality of sleep is important too. Try to make sure you get uninterrupted sleep.
  • The best time to sleep is between 10 pm- 7 am. That is how your body’s natural rhythm works.

Trigger # 3: Stress

Stress induced obesity is not a myth.

Stress takes a huge toll on your body and eating patterns take a hit too.

The biggest reason for stress induced overeating is increased cortisol levels. Swedish researchers have found that increase in cortisol increases leptin resistance too (34).

Researchers at the National Institutes of Health, USA found another way stress changes eating behavior. Stress increases NPY level. NPY relieves stress by initiating a rewarding activity - eating (35)!

What you could do to reduce stress-related eating:

  • Practice mindfulness, meditation and yoga.
  • Get adequate sleep.
  • Do not snack when you are stressed, you will very likely make the wrong choices.
  • Exercise regularly as it keeps cortisol levels down.
  • Practice breathing exercises.


Hunger Hormones in Detail

Hormone # 1: Leptin

Leptin is your body’s major satiety hormone.

It sends your brain a “stop signal” when you are eating and thereby controls your food intake.

Leptin targets a part in your brain called the hypothalamus. Within your hypothalamus, leptin signals that you have eaten enough and now is the time to stop. It also boosts your metabolism and makes you burn more calories than usual (2-6).

Leptin is a product of your body’s fat cells - adipocytes (7-8).

There is a direct link between the amount of body fat you have and leptin levels. The bigger your fat stores; the higher the levels of leptin in your body (9). Thus if you’re obese, you should feel less hungry.

However, the leptin situation is a little more complex.

In fact, it may become more difficult for people to control food cravings with increasing weight.

Why is that? Aren’t the raging leptin levels supposed to curb your appetite? Well, yes, but you have developed a condition called “leptin resistance”. 

No matter how much leptin your body produces, it is an absolute waste if your body cannot put it to a good use. That is the general idea behind leptin resistance.

When you become resistant to leptin, your brain stops responding to even to the highest of leptin levels (10-12). Researchers at the Thomas Jefferson University, Philadelphia made a startling discovery. They found leptin levels can be 318% higher in obese when compared to lean subjects (13).

In a nut shell; the more weight you gain, the less sensitive your body and brain become to the effects of leptin. You get into a perpetual cycle of eating more, gaining more weight and becoming more resistant to leptin. 

Hormone # 2: Ghrelin

Ghrelin is the major hunger stimulating hormone. Its action is more or less opposite to leptin. The cells in your stomach release this hormone in response to recent food intake (14). It has both short and long terms effects on your eating patterns and metabolism.

When you have not eaten in some time, your stomach releases ghrelin. Ghrelin then acts on your stomach itself and empties it further. Once your stomach is empty, it signals your brain that now is the time to fill up your tanks (15)! That is its short term effect.

In the longer run; not only does ghrelin make you eat more, but makes you lose less fat as well. In other words, it makes you put on more weight (16).

How obesity alters your ghrelin levels in the longer run? Spanish researchers showed that ghrelin levels fall by 50% in overweight individuals (17).

If your ghrelin level falls as you weigh more, then why does your hunger worsen?

The answer, again, is leptin resistance.

Although your ghrelin levels fall significantly, your body stops responding to leptin altogether.

The unopposed action of the remaining ghrelin makes you eat more than you should.

Hormone # 3: Pancreatic Peptide (PP) Family

This family contains a lot of important hormones, but the most important are: Peptide YY (PYY) and neuropeptide Y (NPY).

PYY is a hormone secreted by your gut. It functions in a fashion like leptin, but targets a different brain area. It is so potent that a single dose of PYY is enough to reduce your appetite by 40% for 24 hours (18)!

Levels of PYY fall as you gain weight (19).

NPY functions in a fashion opposite to PYY. It is a potent appetite inducer. It is so potent that mice given NPY preferred sugar over sex! It makes you eat more and increases your body fat content too (20).

Levels of NPY increase as you gain weight.

Hormone # 4: Cortisol

Do you tend to eat more when you are stressed? The one word answer is “cortisol”. Your adrenals produce this hormone when you are under stress.

Stress can make you eat more for several reasons (21-22).

First, it is a defense mechanism - the fight or flight phenomenon. It gives you energy to either fight or flee.

Second, eating causes the release of calming brain chemicals like dopamine. These chemicals counter the effects of cortisol and stress.

The participants of the UCSF Health Psychology Program were studied for their eating patterns during stressful situations. Under stress, participants ate more and craved for sugary stuff (23).

Also, researchers found a relationship between higher cortisol levels and impulsive snacking (24).

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  1. Appetite regulation and weight control: the role of gut hormones
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