Originally by Margaret Groves, ZRT Laboratory. Reproduced with permission. Last reviewed: May 2026.
Practical Takeaway: Imbalances in estrogen, testosterone, progesterone and cortisol, brought on by such factors as ageing, diet and the stresses of modern life, have contributed to the obesity epidemic. Our bodies have also not adapted hormonally to the challenges of regulating fat stores when presented with excessive levels of highly refined foods found in the Western diet.
Are Hormones Making Us Fat?
As the incidence of obesity climbs ever higher in the United States and other industrialised countries around the world, so does the number of theories on what are the causes and solutions to the problem. The science on hormones and obesity becomes ever more specialised as researchers debate the possibility of a genetic predisposition, a lifestyle effect, a socioeconomic effect, or an ethnic component.
People struggling to lose weight receive a plethora of dietary advice – eat low carb, eat more whole grains, eat low fat, eat less meat, eat more protein, etc., and no one seems to agree on the best diet for weight loss. But are we becoming too focused on the details and losing sight of the big picture about how our bodies really work?
The whole panoply of bodily functions related to hunger and satiation is orchestrated by chemical messengers produced in response to messages from the brain as well as external stimuli. These chemical messengers are known as hormones. So can it be argued that "my hormones are making me fat"? This blog looks at one family of hormones — the steroid hormones — that have been closely linked with how your body manages weight, and when out of balance may result in weight gain.
This family of steroid hormones can be grouped into the sex hormones and adrenal hormones. The sex hormones include the estrogens (estradiol, estrone, and estriol), progesterone, and testosterone. The adrenal hormones include DHEA and cortisol.
Sex Hormones and Body Fat Distribution
Estrogen & Testosterone
Estrogens are known as the female sex hormones and testosterone as the male sex hormone. While both estradiol and testosterone have a wide variety of functions in both sexes, women in their youth have about ten times more estrogen than men, and men have about ten times more testosterone than women. These stark differences define many of the characteristics that make men and women look and behave differently, including the way body fat is distributed.
Women tend to have fat stores under the skin (subcutaneous fat), around the hips and in the breasts. When estrogen levels are high, excessive fat deposition occurs primarily around the hips and thighs — the typical pear-shaped body type, referred to as "gynoid obesity." Normally healthy men have very little estrogen and subcutaneous fat; when they gain weight it tends to be in the belly, known as "visceral fat" or "central weight gain" — the apple-shaped "android" obesity.
The picture is more complicated in postmenopausal women, when estrogen levels become very low while testosterone continues to be produced from the ovaries and adrenals. This shift in the estrogen/testosterone ratio in favour of testosterone dominance tends to promote male-type body fat distribution. Women who gain weight during and after menopause often find their waistline thickens and they become more apple-shaped than pear-shaped. The same effect is seen in women with polycystic ovarian syndrome (PCOS), who over-produce androgens. Studies of estrogen replacement therapy in postmenopausal women consistently show it can prevent central weight gain by maintaining a relatively higher level of estrogens than testosterone.
Fat tissue itself is an endocrine (hormone-producing) organ. It contains the enzyme aromatase, which converts testosterone to estradiol and androstenedione to estrone. In obese postmenopausal women, estrone can become the predominant circulating estrogen rather than estradiol — estrone is about ten times less potent than estradiol and its presence is a hallmark of menopause.
If you suspect an imbalance in your sex hormones, our Weight Management Profile Test measures estradiol, testosterone, progesterone, DHEA and cortisol from the comfort of home.
DHEA
DHEA (dehydroepiandrosterone) is the precursor for the production of estrogens and testosterone in tissues where they are needed, and it therefore circulates in the body in significantly greater quantities than the other steroid hormones. Studies of DHEA supplementation have found no significant effect on body weight, but one of its natural metabolites, 7-keto DHEA, is known to increase the metabolic rate and has been found to help with weight loss.
Progesterone
Progesterone is well known for its ability to balance and optimise the effects of estrogens. With each monthly cycle, estradiol stimulates the proliferation of breast epithelial cells and those of the reproductive tissues. Progesterone produced in the second half of the menstrual cycle then slows the estrogen-stimulated proliferation, allowing for tissue specialisation and differentiation. For the same reason, progesterone is needed to balance estrogen replacement therapy to prevent excessive growth of the uterine lining and reduce the risk of endometrial cancer.
Synthetic progestins are used for this purpose, but while they effectively suppress endometrial proliferation they have been found to have adverse effects in other areas, notably the cardiovascular system and the breast. Natural progesterone is without these adverse effects and indeed has many beneficial effects in the body. However, some women find it can contribute to weight gain or bloating. Studies have found that women tend to have an increase in appetite and food intake in the latter half of the menstrual cycle and during pregnancy, when progesterone levels are higher than usual.
Some forms of progesterone replacement therapy may lead to excessive progesterone levels that can increase the risk of insulin resistance, which will promote fat storage rather than utilisation for energy. It is important to monitor progesterone levels during supplementation to ensure they are not outside a physiological range and are well balanced with estradiol and testosterone. Bloating or weight gain could mean you are using too much progesterone.
Cortisol, Stress and Weight Gain
How Cortisol Drives Fat Storage
Cortisol is an adrenal hormone essential for blood glucose regulation, fat storage and utilisation, and control of other body functions like the immune system. Cortisol is released from the adrenal glands in response to stressors sensed by the brain — including low glucose levels, emotional or physical stress, or invasion of the body by pathogens.
Cortisol mobilises glucose from the glycogen stores in the liver to be used as short-term energy for the muscles. While normal physiological levels of cortisol are essential to survival, excessive levels caused by chronic stressors shut down non-essential body functions such as the immune system, and suppress the production of other hormones including sex hormones, growth hormone, and thyroid hormones.
When stressors are present for extended periods, we develop a chronic stress condition with persistently elevated cortisol levels. The effects of cortisol on blood sugar result in an increased appetite — particularly for carbohydrates ("stress eating") — and storage of more glucose as fat, especially in the visceral area, which has more cortisol receptors than other types of fat tissue. Stress-related weight gain can be addressed by finding and reducing sources of stress, as well as relaxation techniques to reduce the harmful effects of stress on the body.
To assess whether elevated cortisol may be contributing to your weight gain, consider our Weight Management Profile Test, which includes a full cortisol diurnal profile alongside sex hormones and thyroid markers.
Conclusions
When you understand more about your body and how it is hormonally regulated, it is easier to see that hormones, when in balance, are friends rather than foes. The entire endocrine system includes many more hormones than are mentioned above, which are involved in metabolic processes and other bodily functions that can affect our weight and overall health. But even taking just the reproductive hormones and cortisol, and a little common sense, we can conclude that:
- We have changing reproductive hormone levels as we age. In our attempts to replenish hormone levels back to youthful levels, we sometimes upset the balance — replacing hormones to levels outside an ideal range — and we do not recognise the effects this hormonal imbalance has on weight gain.
- Weight gain itself affects hormone balance.
- Our bodies have highly efficient stress responses, but the extreme, prolonged stresses of modern life have created an unhealthy hormonal imbalance (excessive cortisol) that has contributed to weight gain.
It is important not to ignore the elephant in the room: the highly palatable and refined foods that dominate the "Western" diet, which are clearly associated with the obesity epidemic. These are not the foods our ancestors ate. Our bodies have not adapted hormonally to the challenges of regulating fat stores when presented with these foods in excess.
Keeping our hormones in balance while maintaining a healthy diet, following an exercise programme, and aiming for a stress-reduced lifestyle is key to optimal wellness and longevity.