What May Be Causing Unexpected Weight Changes?

Unexplained weight gain or loss can be a cause of concern. Experts from Keck Medicine of USC share possible explanations.

Obesity, PCOS or thyroid issues

• Thyroid hormone levels
• Excess cortisol
• Polycystic ovarian syndrome
• (PCOS)
• In rare cases, an insulin-secreting tumor
• Obesity in general

“If someone who is overweight or obese loses weight, their resting metabolic rate decreases and their appetite increases, which is a big reason people end up regaining weight,” says endocrinologist Alyssa Dominguez, MD.

“Your thyroid is another culprit of weight fluctuations. If thyroid hormone levels are abnormally high, they can cause weight loss. If they’re too low, they can cause up to 10 pounds of weight gain.”

Cancer

• Colorectal cancer
• Gastric cancer
• Pancreatic cancer
• Other types of cancer, such as leukemia

“Many cancers can cause weight loss,” says colorectal surgeon Joongho Shin, MD. “Many forms of it induce a type of immune response that results in decreased appetite, fatigue, night sweats and weight loss. So, unintended weight loss should raise a red flag.”

Psychiatric conditions

• Eating disorders
• Mood and anxiety disorders, such as major depressive disorder
• Grief
• Substance abuse disorder

“Changes in appetite and weight occur across different types of eating disorders,” says psychologist Kathryn Smith, PhD. “Mood also has a powerful effect on appetite and weight change, which may not be intentional. Stress can increase cortisol, which can affect appetite and eating, so there’s a very strong connection between the mind and body with respect to weight fluctuations.”

Digestive problems

• Constipation
• Water retention
• Certain drugs, such as steroid, antidiarrheal or diabetes medications

“High-protein diets are very popular right now, and they can be associated with constipation, which can lead to a few pounds of temporary weight fluctuations,” says gastroenterologist Danse Bi, MD. “If you’re on a high-protein diet, you should make sure you’re eating enough fiber and vegetables and drinking enough fluids.”

Menstrual cycles, perimenopause and menopause

• Menstrual cycle hormone changes
• Menopause
• Perimenopause
• Endometriosis
• Pregnancy and postpartum

“Menopause is associated with slow, gradual weight gain due to changes in metabolism that happen because of declining hormone levels,” says gynecologist Anna Reinert, MD. “You can try to reverse some of those hormone level changes with hormone replacement therapy, but it doesn’t work for everyone.”

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