Weight loss and weight gain are controlled by more than just calories in and calories out – your hormones play a major role, too.
“In one way or another, hormones control almost every aspect of weight gain and weight loss – considering they affect your metabolic rate, appetite, muscle mass, ability to use glucose for energy, stress levels, sleep and amount of water retention,” says Dr. Josh Axe, D.N.M., C.N.S., D.C., founder of Ancient Nutrition and DrAxe.com.
Key hormones that can affect your weight include ghrelin and leptin, the “hunger hormones”; “stress hormones” such as cortisol; triiodothyronine and thyroxine, two hormones produced by the thyroid that affect the metabolism; testosterone, progesterone and estrogen, and insulin, which affects the way glucose (a.k.a. sugar) is stored in the body. We’ll get into all of this below.
Thyroid, insulin, and hunger hormones
Hormones produced by the thyroid, Axe says, affect your metabolism and your ability to use energy. If you’re concerned you may have a thyroid issue, consult your doctor.
Insulin, on the other hand, is directly related to how our body stores and processes sugar. Axe explains: “Insulin controls the amount of glucose used by your muscles, stored in your liver or turned into fat to be stored in your cells.”
And then there are the hunger hormones: ghrelin and leptin. They control how hungry or full you feel, Axe says.
“Ghrelin and leptin work together to tell your body when it’s time to eat and when it’s time to put the fork down,” says Amanda A. Kostro Miller, RD, LDN, who serves on the advisory board for Smart Healthy Living. “Ghrelin is the hunger hormone that will entice a person to eat. Leptin is a hormone that inhibits hunger in your overall lifestyle.”
She adds that it’s important to pay attention to your hunger and fullness cues when you are eating, “otherwise, we may ignore the signals of these hormones. Ignoring leptin’s signals can lead to overconsumption of calories, leading to weight gain.”
Cortisol, Axe explains, affects the body’s mechanisms for storing fat, particularly around the abdomen, as well as hunger levels. Cortisol, he says, can make you crave more rewarding, high-calorie foods.
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“Testosterone impacts how your body stores muscle versus fat,” Axe says. “Testosterone is a ‘masculine hormone’ (although also produced by women) that contributes to muscle growth and supports a healthy metabolism. In general, low testosterone can lead to issues like muscle loss, weight gain, fatigue, and mood-related problems, not to mention low libido and erectile dysfunction.”
Kostro Miller notes that the relationship between testosterone and weight can go the other way, too: “Being overweight or obese can cause alterations in testosterone, fertility, and sperm count in men.
“But,” she says, “achieving a healthy weight and eating a nutritious diet can help create a more fertile environment for reproduction.”
She adds, “As men age, the decline in testosterone often leads to a decline in lean muscle mass and an increase in fat mass, but getting adequate protein and maintaining a consistent weight training exercise routine can help preserve muscle mass.”
If you’re a person who menstruates, you’ve probably noticed weight fluctuations during your cycle, bloating and/or cravings. This is all related to the hormone changes in your body during that process.
Some of the weight fluctuations during menstruation are due to fluid shifts and are temporary, Kostro Miller says, noting that cravings during that time of the month can lead to overeating.
Kostro Miller also points out a hormonal disorder connected with menstruation – polycystic ovarian syndrome (PCOS). Those who have it often struggle with achieving or maintaining a healthy weight, she says, and should consult a doctor.
Axe adds that changes in reproductive hormones that determine the menstrual cycle can be negatively affected by problems with the hypothalamic-pituitary-adrenal axis.
The HPA axis “describes a group of connected endocrine glands in the body that all communicate with one another and control hormone output,” he says.
“A woman is more likely to experience strong and noticeable PMS [premenstrual syndrome] symptoms, including weight gain due to water retention, if she’s experiencing some HPA dysfunction throughout the month. This might be due to high levels of cortisol caused by chronic stress or sleep deprivation.”
HPA dysfunction, he explains, can result in either too much or too little estrogen in relation to the body’s levels of progesterone. “When these two hormones aren’t in balance before menstruation, PMS symptoms might include holding onto more water, having food cravings, experiencing mood swings and fatigue, and not sleeping well. All of these may lead to weight gain, whether just temporarily or possibly long term.”
In general, he says, someone dealing with “estrogen dominance” and low progesterone, may have a harder time losing weight. If these symptoms occur throughout the month, he advises consulting a doctor for hormone testing.
“If before a woman’s period she notices she gets slightly bloated and may gain one or two pounds temporarily, this probably isn’t something to worry about,” he adds. “This is considered a normal fluctuation and is simply the result of the way that hormones affect a woman’s uterine lining, blood and fluid levels.”
Transitioning into perimenopause and then menopause can also affect weight loss and weight gain.
“Part of the natural aging process is losing lean muscle mass and getting more fat mass,” says Kostro Miller. “You can’t completely change natural aging, but maintaining adequate protein intake and resistance training can help preserve lean muscle mass more effectively.
“Along with the potential for weight gain and loss of lean muscle mass, you may notice that your body changes where it holds fat as you go into menopause and after menopause,” she says. “Instead of hugging fat around your hips, you may notice more weight gain in your abdomen that was not present before.”
A lot of this is tied to the hormone estrogen:
“Estrogen levels drop during menopause, which affects many bodily functions – including bone and muscle mass as well as insulin sensitivity,” Axe says. “As levels decline, a woman may become more susceptible to gaining weight and have a harder time losing weight because she’ll be less insulin sensitive (meaning fat can be stored more easily) and experience a bit of a dip in metabolic rate.”
Other hormones may decline at this point in life, too, he says, such as hormones produced by the thyroid. “Depending on a woman’s stress levels, cortisol might also increase. Together, these factors can make it hard to keep weight off, despite trying to live a healthy lifestyle.”
Most of the ways hormones affect our weight are just natural parts of life, but if you are concerned you may have a hormone imbalance, talk to your doctor. Always listen to your body.