Hormones and Weight Change

Hormones play an important part in regulating the metabolisms of our bodies. Unfortunately, there is some misinformation about their role in weight gain and loss — like whether or not fat cells store hormones. While cells can produce and respond to hormones, no cell can store them. Think of hormones as messages sent through the bloodstream, changing the metabolic function of cells at that receive them.

Four hormones in particular regulate fat metabolism: insulin, cortisol, leptin, and estrogen.


Insulin regulates whether your body uses glucose or fat for fuel. When your body is producing a low level of insulin, the liver responds by turning on the fat-burning system. When levels are too high, sugar will always be prioritized and fat is instead stored for later use.


Cortisol is regulated by the amygdala, the fear center of your primal survival brain. It also works to turn off fat burning in favor of burning glucose. Since glucose is converted to energy faster than fat, this helps quickly fuel your fight-or-flight system. Cortisol also creates cravings for foods high in sugars and carbs in order to get that fuel. That’s why it’s so hard to resist junk food when you’re stressed. When you find yourself reaching for high carb foods while stressed, remember the craving is hormonally driven and not by any demons.


Leptin regulates your energy consumption by inhibiting hunger. In a person with a healthy energy-balance system, fat cells will be refilled with fat as they eat. When the cells are full, they produce leptin, which travels to the brain and instructs it to stop the hunger message it had been sending out.

People who are insulin-resistant are often leptin-resistant as well, meaning the message to inhibit hunger isn’t as strong.


Estrogen is the primary female sex hormone and is responsible for the development and regulation of the female reproductive system and secondary sex characteristics. It also plays a large part in many other functions, including mental health and fat storage.

Estrogen and Mental Health

Estrogen is considered to play a significant role in women’s mental health. Sudden estrogen withdrawal as well as periods of low or fluctuating estrogen levels can contribute to lowered moods and depression. These states can also induce cravings and inhibit the production of dopamine (a neurochemical associated with reward), serotonin (well-being and relaxation), and GABA (relaxation).

Estrogen and Fat Storage

In females, estrogen is primarily produced by the ovaries, the placenta (during pregnancy), and in smaller amounts by the liver, the adrenal glands, and the breasts. However, fat cells also produce estrogen. Because estrogen promotes fat storage, the production of estrogen by fat cells increases as body fat increases — creating a vicious runaway effect. This is one of the reasons that it can get harder and harder to lose weight once you’ve put it on.

When at a good level of weight loss ketosis, the impact of estrogen is lessened because your fat-burning system is fully activated. The estrogen competes with the fat-burning, meaning less and less of the fat actually ends up deposited.

Estrogen and Exercise

In the first two weeks of the menstrual cycle (with day one being the start of your period), your body’s production of estrogen is at its lowest — but this also means that your ability to burn fat is at its highest! Try pushing your cardio and resistance workouts during these two weeks to burn extra fat. However, if you are on any sort of hormonal therapy or contraception, your estrogen production will be increased, likely preventing you from taking advantage of these low points. You can learn more about weight loss and your period here.