Causes of Weight Gain and Obesity 

Causes of Weight Gain and Obesity 

Obesity is a growing problem in the world.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, nearly 2 in 5 adults in the US are obese (1).

But what is exactly obesity?

Obesity is defined as having a body mass index (BMI) of 30 or greater.

A BMI of 30 means that a person has about 30 percent more body fat than what is considered normal. (2)

The problem?

Obesity puts people at risk for a host of chronic health conditions such as heart disease, stroke, type 2 diabetes, depression, and certain types of cancer. (3, 4)

So, what causes weight gain and obesity?

We often hear people say: “I’m eating less and exercising more, but I’m not losing weight.

What am I doing wrong?”

The thing is, weight gain and obesity are often caused by things beyond our control, such as:

1. Hormones

Hormones play a big role in weight regulation.

Changes in hormone levels can lead to weight gain.

For instance, during menopause, many women experience a decrease in the hormone estrogen.

This can cause weight gain, particularly around the waist. (5)

Other hormonal imbalances, such as an overactive thyroid gland or Cushing’s syndrome (a condition that occurs when the body produces too much of the stress hormone cortisol) can also cause weight gain. (6, 7)

2. Genetics

Weight gain and obesity often run in families.

For instance, if your parents or grandparents are obese, you’re more likely to be obese as well.

Researchers have found that certain genes are associated with increased body weight.

For example, the FTO gene has been linked to obesity. (8)

People who have this gene are more likely to be overweight or obese.

Obviously, we can’t change our genes.

But, if weight gain and obesity are common in your family, it’s important to be extra vigilant about following a healthy lifestyle.

3. Medical conditions

Certain medical conditions can also lead to weight gain and obesity.

For instance, polycystic ovary syndrome (PCOS) is a condition that affects women’s hormone levels.

PCOS can cause weight gain, irregular periods, and infertility.

Other conditions that can cause weight gain and obesity include insomnia, hypothyroidism, Cushing syndrome, diabetes, and depression. (9, 10)

4. Certain medications

You heard about how hormones can cause weight gain, right?

Well, some medications can also affect hormone levels, which can lead to weight gain and obesity.

For example, birth control pills and antipsychotic drugs are known to cause weight gain.

Other medications that can lead to weight gain include steroids, insulin, and some antidepressants.

Even over-the-counter medications like antihistamines can cause weight gain. (11)

5. Poor sleep

Most people need seven to eight hours of sleep per night.

But, according to the National Sleep Foundation, nearly one-third of Americans don’t get enough sleep. (12)

Lack of sleep can lead to weight gain and obesity.


Poor sleep can disrupt the hormones that regulate appetite, leading to increased hunger and cravings for unhealthy foods.

Plus, when you’re tired, you’re more likely to make poor food choices and have little energy for physical activity.

6. Food addiction

First off, let’s get one thing straight: food addiction is a real thing.

And it can lead to weight gain and obesity. 

People who are addicted to food often eat even when they’re not hungry.

They may also continue eating even after they’re full.

To make matters worst, people with food addiction often crave certain foods, such as sugary or junk foods.

And they may feel out of control around these foods.

If you think you may be addicted to food, talk to a doctor or dietitian.

They can help you develop a plan to overcome your addiction and achieve a healthy weight.

7. Stress

We all know that stress can lead to unhealthy behaviors, such as overeating, smoking, and drinking alcohol.

But did you know that stress can also cause weight gain?

When you’re stressed, your body produces the hormone cortisol.

Cortisol can lead to increased hunger and cravings for sugary and fatty foods. 

It can also promote the storage of fat in the abdominal area. (13)

If you’re stressed, find healthy ways to cope, such as exercise, meditation, and spending time with friends and family.

Learn more: 10 Simple Ways to Reduce Stress Quickly

8. Age

As we get older, our metabolism slows down.

This means we burn fewer calories, and it becomes harder to lose weight.

Plus, as we age, we tend to become more sedentary.

We may not be able to do the things we used to do, such as play sports or run around with our kids.

And we may not have the same motivation to be active.

All of these factors can lead to weight gain. 

9. Lack of physical activity

If you’re not active, you’re more likely to gain weight.

Physical activity helps to burn calories and keep your weight in check.

Adults should aim for at least 150 minutes of moderate-intensity aerobic activity, such as brisk walking, per week.

Or, you can do 75 minutes of vigorous-intensity aerobic activity, such as running, per week.

You can also do a combination of moderate- and vigorous-intensity activity.

Besides, adults should also do strength training, such as lifting weights, at least two days per week. (14)

Causes of Weight Gain and Obesity 


Weight gain and obesity can be caused by a variety of factors, including hormones, certain medications, and poor sleep.

Other causes include stress, age, and lack of physical activity.

If you’re struggling to lose weight, talk to a doctor or dietitian.

They can help you develop a plan to reach your weight loss goals.

Do you want to know more about how to lose weight without dieting?

Read this article next: 6 ways to lose weight without dieting