Unexplained Weight Gain: Insights & Steps to Address It

Weight gain is an increase in body weight. It can be due to an increase in muscle mass, fat deposits, or excess fluid in the body. Body Mass Index (BMI) is a commonly used tool to categorize individuals based on their height and weight. It is an easy and low-cost method to identify individuals who are overweight and obese (excess weight), including adults and children, which may lead to health interventions. BMI is calculated by dividing the weight in kilograms by the height in meters squared. 

Note: In children and teenagers, the weight status is calculated based on the CDC’s growth charts.

What Is Considered Rapid Weight Gain?

According to the American Heart Association, weight gain of more than 2 or 3 pounds in 24 hours or 5 pounds in a week is considered rapid weight gain. This can be a sign of a serious underlying medical condition, such as worsening heart failure. 

Note: It is common to have some weight fluctuations. An increase or decrease in body weight by a few pounds (2 to 4 pounds) can occur with changes in diet and activity levels over time. However, if the extra pounds come on suddenly or quickly and cannot be explained by consuming more calories or being less active, then the cause of weight gain should be evaluated.

Why Am I Gaining Weight So Fast?

The most common cause of weight gain is an unhealthy lifestyle (eating too many calorie-dense foods and not getting enough exercise). However, sometimes, an underlying health condition or side effects of medications can result in weight gain.

Common Misconceptions  

Myth: Dieting can help you lose weight quickly.

Fact: The body needs a balanced diet for proper nutrition and health. Restrictive diets can be harmful by preventing your body from getting important nutrients. Yo-yo dieting (cycling through weight loss and weight gain) has been linked to an increased risk of cardiovascular disease.

Myth: Cutting back on carbs can help you lose weight.

Fact: Eating fewer simple carbohydrates (found in processed and sugary foods like cookies and candies) can help with weight loss. However, complex carbohydrates (whole grains, fruits, vegetables) contain many important nutrients, including vitamins, minerals, and fiber, and should be part of a healthy diet.

Myth: Slow weight loss is the only healthy way to lose weight and keep it off.

Fact: It is true that many people who lose weight quickly gain it back. However, rapid weight loss can work for some people, especially people with severe obesity. It’s best to avoid fad diets that make tall promises. Work with your healthcare professional to develop a healthy eating plan that is sustainable in the long term. 

Underlying Health Conditions: What Diseases Cause Rapid Weight Gain? 

Thyroid Issues  

The thyroid is a butterfly shaped gland in the neck that makes thyroid hormone. This hormone regulates many important functions in the body including metabolism. 

Hypothyroidism (underactive thyroid gland) can cause weight gain by causing the body to burn fewer calories and retain salt and water. About 5-10 pounds of weight gain is common in people with hypothyroidism, but it varies from person to person. More severe hypothyroidism causes more weight gain. 

Hyperthyroidism (overactive thyroid gland) usually causes weight loss. However, people with hyperthyroidism also have an increased appetite and may gain weight, depending on how many calories they consume. 

Polycystic Ovary Syndrome (PCOS)  

Polycystic ovary syndrome (PCOS), also called polycystic ovarian disease (PCOD), is a common hormonal condition in women of reproductive age. It is a leading cause of infertility. Symptoms include irregular menstrual periods, acne, excessive facial hair, hair thinning, and male pattern baldness due to higher levels of male androgenic hormones in the body.

PCOS can cause an increase in weight because many people with this condition also have insulin resistance (inability to pull glucose from the blood into the cells for energy). Insulin resistance is a major contributing factor to obesity and type 2 diabetes (high blood sugar).

Cushing’s Syndrome and Unintentional Weight Gain

Cushing’s syndrome is a condition in which there is too much cortisol in the body. High levels of stress hormone cortisol can lead to weight gain in the trunk area with thin limbs, moon facies (weight gain in the face), and a buffalo hump (fat deposit between the shoulders). Other symptoms may include acne, stretch marks, thinning of the skin, easy bruising, and slow wound healing.

Studies have found people with Cushing’s syndrome can have extra weight gain of 4-5 pounds over a 6-month period compared to people with similar dietary patterns and physical activity levels who don’t have Cushing’s syndrome.

Heart Failure

People with congestive heart failure can gain weight due to fluid retention. This occurs because the heart is not pumping blood as well as it should. It can result in rapid weight gain, swelling in the ankles and feet, swelling in the abdomen, and breathlessness due to fluid in the lungs. Rapid or sudden weight gain of more than 2 or 3 pounds in 24 hours or 5 pounds in a week can be a sign of worsening heart failure.

Kidney Disease 

When the kidneys are not working properly, they cannot make enough urine, causing the body to retain fluid. This fluid retention can lead to swelling and weight gain. Unintentional weight gain can be a symptom of kidney problems such as chronic kidney disease and nephrotic syndrome (excess protein excretion).

Diabetes: Why Am I Getting Fat When I Don't Eat Much?

People with undiagnosed diabetes may experience weight loss without trying due to frequent urination, loss of sugar in urine, and dehydration. However, after a diagnosis of type 1 or type 2 diabetes is made and hydration improves, it can result in some weight gain. Over time, as less sugar is lost in urine, weight gain can continue unless steps are taken to prevent it with healthy lifestyle changes. In addition, insulin therapy can lead to weight gain.

Obstructive Sleep Apnea

Obesity is a risk factor for obstructive sleep apnea (OSA), a type of sleep-disordered breathing. However, research also suggests that OSA can lead to weight gain. Scientists have found people with sleep apnea have high levels of a hormone called leptin as well as leptin resistance. This prevents feelings of fullness after eating, leading to overeating and weight gain.

Other Potential Causes of Sudden Weight Increase  

Medication Side Effects  

Certain medications can cause weight gain as a side effect, either by causing fluid retention or by increasing appetite and hunger. Examples include:

• Antipsychotic drugs such as olanzapine (Zyprexa) and risperidone (Risperdal).

• Antidepressants such as paroxetine (Paxil) and amitriptyline (Elavil).

• Antiepileptic drugs such as valproate and carbamazepine.

• Mood stabilizers such as lithium.

• Antihypertensive drugs such as beta-blockers, for example, atenolol (Tenormin) and metoprolol (Lopressor).

• Antihistamines such as diphenhydramine (Benadryl).

• Steroid medications such as prednisone, dexamethasone, and prednisolone.

• Diabetes medications such as insulin, sulfonylureas (glipizide, glyburide), and thiazolidinediones (rosiglitazone (Avandia), pioglitazone).

Hormonal Imbalances, Menopause, and Weight Gain: Why Am I Gaining Belly Fat All Of A Sudden?

Many women gain weight while going through menopause. Studies estimate that weight gain occurs at an average rate of 1.5 pounds each year in the 50s. This happens because of hormonal changes (falling estrogen levels). It can lead to central obesity (weight gain in the belly area). 

But hormonal changes are not solely responsible for gaining weight during menopause. Genetics, lifestyle factors, and age-related changes such as a slower metabolism also play a role.

Metabolic Syndrome

Metabolic syndrome is a group of conditions that increase the risk of diabetes, heart disease, and stroke. They include high blood pressure, high blood glucose, high triglyceride levels, low HDL (high-density lipoprotein) or the “good” cholesterol, and abdominal obesity (belly fat). A noticeable sign of metabolic dysfunction is weight gain (obesity is a risk factor).

Age-Related Physiological Changes  

Starting in middle age, our bodies lose muscle mass at a rate of 1% each year. Smaller muscles consume less energy, and the extra energy is stored as fat. So, unless you eat fewer calories, age-related muscle loss, fat storage, and changes in body composition can lead to weight gain. 

In addition to less muscle mass, metabolism slows with age, affecting how quickly the body burns calories. 

Also, lower levels of female and male sex hormones in older women and men can lead to an increase in body fat. 

Psychological Factors  

Mental health conditions and medications used to treat them can cause weight gain, for example, anxiety, depression, bipolar disorder, binge eating disorder, and others.

Lifestyle Factors Contributing To Gaining Weight

Dietary Habits  

A high-calorie diet consisting of ultra-processed foods (frozen dinners, processed meats, and savory snacks like potato chips) that contain unhealthy fats is a leading cause of weight gain and obesity. Consumption of sugary foods like candies, cakes, cookies, ice creams, and sugary beverages is also linked to weight gain.

Sedentary Lifestyle  

Inactivity or lack of physical exercise is a common contributor to weight gain. Examples of sedentary activities include working a desk job, using a computer, or driving.

Sleep Patterns  

Poor sleep and sleep deprivation can disrupt hormones that regulate appetite. In other words, not getting enough restful sleep at night can lead to higher levels of hunger hormones in the body, which can promote overeating and weight gain.

Stress and Mental Health  

Chronic stress can lead to high levels of the stress hormone cortisol made by the adrenal glands. This can lead to an increase in appetite and storage of unused energy as fat. In addition, stress can lead to overeating of unhealthy “comfort foods.” People who are depressed may likewise overeat and lose interest in physical activity, both of which can result in gaining weight.

Quitting Smoking

Many people gain weight after they quit smoking, to the tune of 5 to 10 pounds in a few months. This occurs because smoking suppresses appetite and nicotine in cigarettes speeds up metabolism. When people stop smoking, they often turn to unhealthy comfort foods to deal with cravings. Together, these factors often lead to an increase in weight after quitting.

Solutions and Management Strategies for Sudden Weight Gain

Consult a Healthcare Professional

If you have experienced sudden or rapid weight gain recently, make an appointment to see your healthcare provider. They can find out if there is an underlying health condition responsible for your gaining weight and develop a treatment plan. They can also refer you to an obesity medicine specialist, if needed, for weight management.

Monitor Dietary Intake  

A balanced, healthy diet, rich in fruits, vegetables, whole grains, legumes, lean protein, low-fat dairy, and healthy fats is the best way to build muscle and avoid gaining weight. To monitor dietary intake, consider keeping a food diary where you record what and how much you eat. Choose healthy foods and snacks over unhealthy ones, and avoid late-night snacking. 

Incorporate Regular Physical Activity  

Regular exercise can help you burn calories, lose pounds, and build muscle strength and muscle mass. Experts recommend 150 minutes of moderate-intensity aerobic exercise each week and strength training at least twice a week. 

Understand Medication Impacts  

If you are taking over-the-counter or prescription medications, talk to your healthcare provider about whether they could be contributing to your excess weight. 

When To Seek Professional Advice  

Persistent Unexplained Weight Gain

Most weight gain is due to unhealthy lifestyle habits. But if you continue to gain weight despite a healthy diet and regular physical activity, consult your healthcare provider. They can find out if an underlying medical condition is causing weight gain. Any sudden weight changes should be evaluated without delay. You should also seek medical care for unexpected weight loss. 

Rapid Weight Gain

If you experience weight gain of more than 2 or 3 pounds in 24 hours or more than 5 pounds in a week, call your doctor. 

Accompanying Symptoms To Watch For 

Seek medical care if you have weight gain accompanied by symptoms such as uncontrolled hunger, constipation, hair loss, skin changes, swelling anywhere in the body, shortness of breath, palpitations, tremors, or vision changes.

How Do You Know If You Have Been Gaining Weight?

You can tell you have been gaining weight by the way your clothes fit and by measuring and tracking your weight on a scale at home.