HORMONES
HOW HORMONES AFFECT WEIGHT
March 18, 2024
Quick Answer
Hormones like leptin, ghrelin, cortisol, insulin, estrogen, and thyroid hormone all help control your appetite, metabolism, and where your body stores fat. When these hormones fall out of balance, from chronic stress, aging, or an underactive thyroid, it becomes much harder to manage your weight no matter how carefully you eat or exercise. Balancing your hormones is often the missing piece for lasting weight change.
Key Takeaways
- Leptin and ghrelin control your hunger and fullness signals
- Cortisol, the stress hormone, encourages fat storage around your belly
- Insulin resistance makes it harder for your body to use sugar for energy, so it stores more fat instead
- Estrogen and testosterone shifts, especially with age, change how and where you store fat
- An underactive or overactive thyroid can cause unexplained weight gain or loss
- Balancing these hormones through diet, exercise, sleep, and medical support when needed can make weight management far easier
Our hormones are closely tied to our weight. Not only does weight significantly affect our hormones but certain hormones can affect how much we weigh. The interaction between our adipose (fatty) tissue and our hormones involves a series of complex feedback loops. For instance, there is a strong correlation between obesity and fertility. Obesity has detrimental effects on every system in our body including our reproductive system and fertility hormones. Due to the hormonal imbalances caused by obesity, obese women have a harder time getting pregnant naturally or through assisted conception compared to women of healthy weights. Women who are obese are also more likely to experience miscarriage and adverse pregnancy complications due to hormonal dysfunction which can prevent ovulation or cause failure in fertility treatments. Obesity is, therefore, a disruptor of female fertility. As expected, weight loss has beneficial effects on reproductive outcomes for these individuals.The obesity epidemic in developed countries, particularly in the U.S., has exploded in the past 50 years. In the 1960s and 1970s, obesity levels changed relatively little as people filled their lives with healthy food and physical activity. By 1980, there was a sharp increase of 13.4% in obesity in adults, and 5% increase in children. By 2008, the prevalence had risen sharply to 34.3% for adults and 17% in children. Fast forward to today and obesity continues to skyrocket, tripling among children, and doubling among adults especially in the most recent years.
With technological advancements, including easy access to cars, planes, trains, computers, and smart devices, people are more sedentary, thereby causing an overall decline in physical activity. About 31% of the global population aged 15 and older do not engage in sufficient exercise. Over time, levels of exercise have declined while the collective intake of certain foods like sugary beverages (particularly sodas) and ultra-processed foods (high in calories, sugar, fat, and salt) has increased drastically. Unfortunately, junk food is often cheap and readily available at fast-food restaurants.
Although about 1.6% of the U.S. adult population struggle with being underweight along with its health challenges, more than a third of adults worldwide are overweight and about 42% of the U.S. adult population is obese. By 2030, an estimated 50% of all U.S. adults will be either overweight or obese and nearly one in four adults will be severely obese.
So what does it really mean to be underweight, overweight, or obese? How do you determine what your ideal weight is? Generally, weight is calculated based on the body mass index (BMI). The BMI is not a perfect measure of the amount of fat in your body; however, it is a universally accepted measure of the best estimate of your ideal healthy weight based on your height and weight:
- Underweight – BMI less than 18.5
- Healthy/Normal – BMI between 18.5 to < 25
- Overweight/Pre-obese – BMI between 25 to <30
- Obese – BMI above 30 or higher
o Class 1 Obesity – BMI of 30 to < 35
o Class 2 Obesity – BMI of 35 to < 40
o Class 3 Obesity – BMI of 40+ (also known as severe obesity)
Which Hormones Affect Weight?
Many hormones, including leptin, ghrelin, cortisol, estrogen, insulin, growth hormone, and thyroid hormone, are directly involved in hormonal weight gain and the broader interaction between weight regulation and the endocrine (hormonal) system.
- Leptin – This hormone is made by fat cells. It enters the bloodstream and travels to the brain where it acts on specific parts of the brain to reduce the urge to eat, thereby reducing a person’s appetite. Leptin also controls fat storage in the body. Since leptin is made by fat cells, it is often higher in obese people; however, despite these high levels of leptin, people who are obese are not as sensitive to the effects of leptin and so they do not feel full, even after a large meal.
- Ghrelin – Ghrelin, famously known as the “hunger hormone,” is made in the gastrointestinal tract. Ghrelin plays a role in regulating your calorie intake as well as your body fat levels. When elevated, this hormone sends signals to the brain to feel hungry. When too much Ghrelin is made, it can slow down metabolism and decrease the body’s ability to burn fat. Ghrelin also stimulates accumulation of abdominal fat.
- Cortisol – Cortisol, commonly known as our stress hormone, does more than just regulate our body’s response to stress. It also stimulates fat and carbohydrate metabolism to increase our energy and our appetite. Too much cortisol increases craving for salty, sweet, and fatty food which can lead to being overweight and obese. Thus, chronically elevated cortisol can lead to overeating and weight gain — often called “cortisol belly” — particularly around the face and abdomen Chronic stress and its effect on cortisol is a common, often overlooked driver of stubborn weight gain, which we cover in more depth in how cortisol and stress shape your body.
SEX HORMONES
Estrogens, testosterone, and progesterone are the main sex hormones responsible for reproductive health in females; however, they also play a role in determining our body fat distribution. Most estrogen is made in the ovaries. In pre-teen girls, higher estrogen levels lead to fat deposition around the breasts, buttocks, hips, and thighs. As women age — particularly through the menopause transition — overall estrogen and progesterone levels decrease. This triggers metabolic changes that reduce metabolism and leads to excessive weight gain — often called menopause weight gain. Levels of estrogen synthesized in the ovaries also decrease with age and eventually the responsibility of production of estrogen shifts to the fatty tissues. High levels of estrogen in fatty tissue leads to the development of obesity-related disorders, such as diabetes, heart disease, and cancer.
Progesterone in high doses, such as found in progesterone implants or injected progesterone contraceptives, does not directly affect weight; however, in some women, progesterone increases appetite, thus leading to over-eating and eventual weight gain. Low testosterone levels are associated with increased fat and obesity because obesity lowers testosterone levels.
- Insulin – Insulin is a hormone produced by the pancreas. It is responsible for the regulation of carbohydrates and metabolism of fat. It stimulates sugar uptake from the blood and is important for maintaining a normal circulation of glucose in the blood. Insulin harnesses our consumed calories and puts them to work in our cells. With obesity, insulin signals are dysfunctional and glucose control is disrupted leading to development of Type II diabetes and metabolic syndrome (insulin resistance syndrome), a group of conditions that increase the risk of heart disease, diabetes, and stroke.
- Growth hormone – This is the hormone that builds bone and muscle and influences a person’s height. Growth hormone also affects our metabolism rate. Individuals who are obese tend to have lower levels of growth hormone compared to people with normal weight. This leads to an imbalance between adipose tissue and lean body mass.
- Thyroid hormone – A change in levels of our thyroid hormones can cause weight gain or weight loss. Low levels of thyroid hormones due to an underactive thyroid (hypothyroidism) can lead to weight gain, while high levels of thyroid due to an overactive thyroid (hyperthyroidism) can lead to weight loss.
How Does Obesity Affect Hormones?
Hormonal imbalance is a significant factor in obesity. People who are obese typically have an imbalance in hormones such as leptin, insulin, sex hormones, and growth hormones which affect metabolism, appetite, and fat distribution. This imbalance further affects metabolism and subsequently causes accumulation of fat. Obesity is the result of too much fat accumulation. Aging is another factor that can lead to weight gain. When women age, their hormone levels change and these changes can promote obesity.
Just as hormones can lead to obesity, obesity can also affect hormones. Fat cells (adipose tissues) are abundant in obese individuals and in obese postmenopausal women, these fat cells are responsible for estrogen biosynthesis. Estrogen is one of the most prominent female sex hormones responsible for many functions. Within the fat cells lie enzymes that can convert other hormones into estrogen. When estrogen dominates the body (estrogen dominance), it can lead to issues such as decreased ovulation, irregular periods, heavy menstrual periods, bloating, hot flashes, difficulty concentrating, fatigue, mood swings, decreased fertility, low libido, insomnia, and weight gain. These overlap with several of the 12 warning signs of hormonal imbalance, so it is worth tracking your symptoms as a full pattern rather than one at a time.
Obesity and excess body fat can contribute to insulin resistance. Insulin resistance is a condition where your cells do not respond well to insulin, and thus, cannot take up glucose from your body. Insulin resistance is caused by obesity, especially too much fat around the abdomen and organs (visceral fat). These fat cells can synthesize hormones as well as other substances that increase the risk of chronic inflammation in the body. Chronic inflammation can lead to insulin resistance, Type II diabetes, and cardiovascular diseases. Losing weight can help the body respond better to insulin. This same insulin resistance is also a hallmark of polycystic ovarian syndrome (PCOS), a common driver of PCOS (recently renamed polyendocrine metabolic ovarian syndrome, or PMOS) weight gain.
How Balancing Your Hormones Can Improve Your Weight
Since there is a significant interplay between your hormones and weight, balancing your hormones can help you maintain a healthy weight, ensure optimal fertility, and promote overall wellbeing. For a deeper, step by step plan, see our full guide on how to reset your hormones for weight loss. Some things you can do to balance your hormone and improve your weight include:
- Increase physical activity – Our bodies are designed for physical activity. Regular physical exercise can optimize the connections between the brain and ovaries to promote ovulation. Just a 5% -10% loss in total body weight can improve fertility outcomes. Exercise also burns calories and can reduce body fat. Less body fat can promote an improvement in estrogen dominance and a reduction in androgen levels in women. Regular movement is also one of the most effective ways to address the stubborn midsection weight gain we cover in getting rid of hormonal belly naturally.
- Improve diet to reduce sugar intake – Insulin is sensitive to your intake of sugar. By eating a healthy diet of complex carbohydrates, proteins, and fats in optimal ratios, you can regulate your insulin levels and moderate its ability to store calories as fat.
- Avoid crash dieting – Crash dieting may result in lowered leptin levels. Lower levels of leptin signal to your body that you have no body fat which, in turn, causes intense hunger and food consumption, naturally leading to weight gain. Instead of crash dieting and causing a leptin imbalance, consider gradually reducing your caloric intake to lose weight for good.
- Discuss hormone regulation with your doctor after menopause – Estrogen in women promotes accumulation of subcutaneous (under the skin) fat. Loss of estrogen with menopause promotes increased central fat which is responsible for increasing the risk of diabetes, hypertension, and cardiovascular disease. Talk to your doctor about ways to offset the loss of estrogen that occurs around menopause. Our guide to a smoother perimenopause transition covers more of what to expect.
- Have your thyroid hormone levels checked – If you struggle with unexplained weight gain as well as other possible symptoms of low thyroid gland function such as dry skin, constipation, cold sensitivity, fatigue, and low mood, see your doctor to ensure your thyroid hormone level is within the range needed to support optimal metabolism.
Hormonal imbalance and obesity act in synergy to produce adverse health outcomes. Offsetting weight gain and fixing hormonal imbalances can reduce your risk of developing diseases such as heart disease, cancer, high blood pressure, and infertility.
Hormones and Weight at a Glance
| Hormone | Where It Is Made | Effect on Weight When Out of Balance |
|---|---|---|
| Leptin | Fat cells | Leptin resistance can leave you feeling hungry even after eating enough |
| Ghrelin | Stomach and gut | Rising levels increase appetite and encourage fat storage around the abdomen |
| Cortisol | Adrenal glands | Chronic stress keeps cortisol high, driving cravings and belly fat storage |
| Insulin | Pancreas | Insulin resistance disrupts blood sugar control and promotes fat storage |
| Estrogen and progesterone | Ovaries and fat tissue | Shifts with age, PCOS, or menopause change fat distribution and appetite |
| Thyroid hormone | Thyroid gland | Low levels slow metabolism and cause weight gain, high levels cause weight loss |
| Growth hormone | Pituitary gland | Lower levels in people with obesity shift the balance toward more fat and less lean muscle |
When to See a Doctor About Weight and Hormone Changes
Most hormone related weight shifts happen gradually and respond well to the changes above. See Doctor P if you notice any of the following.
- Losing or gaining more than 5% of your body weight within a few months without changing your diet or activity level
- Persistent fatigue, cold sensitivity, or constipation alongside weight gain, which can point to an underactive thyroid
- Rapid weight gain with a rounded face, new stretch marks, or high blood pressure, which can signal excess cortisol
- Irregular or absent periods along with weight changes, which can point to PCOS or another hormonal imbalance
- Excessive thirst, frequent urination, or blurry vision alongside weight changes, which can signal a blood sugar problem
Doctor P can order the right bloodwork to find out which hormone is driving your symptoms instead of leaving you to guess. For a full rundown of common patterns, see our guide to common hormone imbalances.
Frequently Asked Questions
Can hormonal imbalance cause weight gain even with a healthy diet?
Yes. When hormones like insulin, cortisol, or thyroid hormone are out of balance, your body can store more fat and hold onto weight even if you are eating well and staying active. Balancing the underlying hormone, not just cutting more calories, is often what actually moves the needle.
Which hormone is most responsible for belly fat?
Cortisol is the hormone most closely tied to abdominal fat. When stress keeps cortisol elevated for long periods, your body tends to store extra fat around your midsection rather than other areas.
Can losing weight fix a hormone imbalance?
Weight loss can improve some hormone imbalances, especially insulin resistance and estrogen dominance linked to excess fat tissue. But some imbalances, like thyroid dysfunction, need direct treatment of the hormone itself, not just weight loss.
Does menopause make it harder to manage your weight?
Yes. As estrogen and progesterone decline during perimenopause and menopause, your metabolism slows and fat tends to shift toward your abdomen. This is a hormonal shift, not a lack of willpower.
How do I find out if a hormone imbalance is affecting my weight?
Bloodwork that checks hormones like thyroid hormone, insulin, and cortisol can identify an imbalance. Doctor P’s Ultimate Hormone Assessment is another good starting point to help you understand your symptoms before your appointment.
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