Cause Of Unexplained Weight Gain: When to see a doctor?

Some people complain about weight gain even when they are eating and exercising the same as always.

Weight Regain After Weight Loss

Let’s look deeper at possible reasons for weight gain.

Underactive thyroid

An underactive thyroid (hypothyroidism) means your thyroid gland is not producing enough thyroid hormones. This slows the body’s metabolism and can lead to weight gain. Although an underactive thyroid can occur at any age and in either sex, it is most common in older women.

Women with hypothyroidism may also suffer from low energy levels or fatigue, dry skin, hair loss, hoarseness, or constipation. Notice any of them and you should book a chat with your doc who can check on your thyroid with a simple blood test if necessary.

Polycystic ovary syndrome

It is an endocrine disorder that throws off the balance of reproductive hormones estrogen and testosterone and can trigger a number of unpleasant symptoms like wacky periods, facial hair growth, and migraines.

PCOS can also change the way your body uses insulin (the hormone that helps turn sugars and starches into energy), which means unexplained weight gain around the mid-section is common.

If your menstrual cycles are off, a gyno will likely take a peek at your hormones to diagnose this one.


Cortisol, the so-called “stress hormone,” increases in our bodies when we’re stressed out. This hormone, in turn, increases our appetite. Add to that the tendency to reach for comfort foods at times of stress, and you have a perfect opportunity for weight gain.


Sleeping too little raises ghrelin, the hormone that signals it’s time to eat while lowering your levels of leptin, the hormone that conveys the “I’m full” feelings. The result: a totally unsatisfying chow-fest the next day. A 2018 study in the journal Sleep found that people who slept just one hour more per week lost more fat than those who slept an hour less. The people who slept less lost less—even though everyone in the study ate the same number of calories, proportionate to their weight at the start of the study.


The transition period to menopause ( which can start in women as early as their mid-30s, but usually starts in their 40s) triggers hormones like estrogen to rise and fall unevenly, which can cue weight gain in some women. (Other signs of perimenopause include irregular periods, hot flashes, mood swings, and a change in your libido—symptoms your doc can usually suss out with her eyes closed.)

Compound perimenopause with the other inevitable body changes that happen with age (like a loss of muscle mass and increase in body fat), and it may feel like the scale’s tipping fast. Talk to your doctor to manage “the change” in stride.



There’s a long list of both prescription and over-the-counter meds that can trigger sudden weight gain or water retention that shows up on the scale as extra poundage. “Antidepressants may affect the appetite center in the brain,” says Rocío Salas-Whalen, MD, an endocrinologist at the Medical Offices of Manhattan (source:

Beta-blockers (meds that reduce blood pressure) can slow your metabolism, and certain steroids (like prednisone—an anti-inflammatory that causes water retention and an increased appetite) can add on pounds. Even OTC antihistamines like Benadryl, can disrupt an enzyme in the brain that helps regulate food consumption, can trigger noticeable weight gain.

A word to the wise: Consult your doctor, who may be able to find a more waist-friendly substitute.

Birth Control Pill

Many women believe taking combination oral contraceptives (birth control pills) causes weight gain. However, there is no scientific evidence this is the case. Some women may have mild fluid retention while taking the pill, but this is usually temporary.

Cushing’s Syndrome

A condition characterized by elevated levels of the hormone cortisol. It can occur if your body makes too much cortisol or if you take steroid medications for asthma, lupus, or arthritis. Cortisol excess can cause weight gain and an increase of fat around the face, neck, waist, and upper back.

Quitting Smoking

People who quit smoking may gain a small amount of weight. The reasons are varied. Without nicotine:

  • You may feel hungrier, although this effect tends to disappear after a few weeks.
  • Your metabolism may decrease.
  • You may enjoy food more or feel it tastes better, which could lead to overindulging.
  • You may eat more high-fat or sugary snacks, or drink more alcohol.

To counteract the lower levels of dopamine once you quit smoking, it’s important to engage in other behaviors, like exercise or meditation, that help release feel-good endorphins and also provide a nice distraction and healthy new habit.


People begin to lose some muscle as they get older, largely because they become less active. Muscles are an efficient calorie burner, so a loss of muscle mass can mean you burn fewer calories.

If you’re eating and drinking the same amount as you always have and are less physically active, this can lead to weight gain. To reduce muscle loss, you should stay active and try to do regular muscle-strengthening exercises.

Fluid retention

Fluid retention can cause you to gain weight as parts of the body become swollen with fluid. Some types of fluid retention are common, for example: standing for long periods
being premenstrual
The swelling can occur in one particular part of the body, such as the ankles, or it can be more general. More severe fluid retention can also cause breathlessness.

When should I see a doctor for sudden, unexplained weight gain?

To begin with, take a look at what your lifestyle’s like. If your diet is poor, it’s normal to gain between half a pound to a pound of weight a week. Your menstrual cycle can also catch your weight to fluctuate between four and five pounds depending on what stage of your cycle you are.

But when is weight gain a cause for concern? If you’re gaining one to two pounds or more a week, and you don’t see the numbers going down, then it might be time to see a doctor.

A doctor can work with you to determine whether an underlying condition is determining your weight gain, and find appropriate remedies to help you maintain a weight that makes you feel good.


The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

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