What causes body aches and weight gain?

September 27, 2025 •

5 min read

According to the CDC, approximately 53% of US adults experienced chronic pain in 2021, and over 40% of adults aged 20 and over have obesity. When these two frustrating symptoms—body aches and weight gain—occur together, they can significantly impact your quality of life. This combination often points to an underlying health issue rather than just a simple lack of discipline. Understanding the root causes is the first step toward effective management and relief.

Quick Summary

Potential culprits for body aches and weight gain range from hormonal disorders like hypothyroidism and PCOS to lifestyle factors such as chronic stress and poor sleep, all of which can trigger metabolic changes and inflammation. Addressing the underlying medical condition is key to managing these interconnected symptoms.

Key Points

Hormonal Issues: Conditions like hypothyroidism, PCOS, and Cushing's syndrome are major drivers of both weight gain and body aches due to their effects on metabolism and inflammation.
Lifestyle Factors: Chronic stress and poor sleep can lead to hormonal changes (e.g., elevated cortisol) that promote weight gain and increase pain sensitivity.
Chronic Illnesses: Fibromyalgia and Chronic Fatigue Syndrome are conditions defined by widespread pain and fatigue, which often lead to inactivity and subsequent weight gain.
Medication Side Effects: Certain medications, including steroids, antidepressants, and some diabetes drugs, can cause weight gain and muscle aches as a side effect.
Nutrient Deficiency: A lack of vital nutrients like Vitamin D can contribute to muscle pain and may be associated with increased body weight.
Interconnected Cycle: In many cases, body aches can lead to inactivity, causing weight gain, which then puts more stress on the body and worsens the pain, creating a feedback loop.

Hormonal Imbalances and Dysfunction

Hormones play a critical role in regulating metabolism, inflammation, and energy levels. When these systems are out of balance, a combination of weight gain and body aches often results.

Hypothyroidism (Underactive Thyroid)

Hypothyroidism is a common condition where the thyroid gland does not produce enough thyroid hormone. This hormone is essential for regulating metabolism. When metabolism slows down, the body's processes are affected, leading to a host of symptoms:

Weight Gain: A slowed metabolism means the body burns fewer calories at rest, leading to weight gain, even with no changes in diet.
Muscle and Joint Aches: Low thyroid hormone levels can cause nonspecific muscle and joint pain, weakness, and stiffness.
Fatigue: Extreme tiredness is a hallmark symptom, often accompanied by feeling cold and experiencing constipation.

Polycystic Ovary Syndrome (PCOS)

PCOS is a hormonal disorder affecting people with ovaries and is a common cause of weight gain. Insulin resistance is a key component, where the body's cells don't respond properly to insulin. The pancreas then produces more insulin, leading to several issues:

Weight Gain: High insulin levels cause the body to store excess glucose as fat, particularly around the abdomen. This makes weight loss particularly difficult.
Inflammation and Pain: The hormonal imbalances in PCOS can lead to chronic inflammation, which is linked to pelvic pain and generalized body aches.

Cushing's Syndrome

This condition occurs due to prolonged exposure to high levels of the hormone cortisol, either from the body overproducing it or from long-term use of steroid medications.

Weight Gain: High cortisol promotes fat storage, especially in the face ("moon face"), neck, and upper back, along with abdominal obesity.
Muscle Weakness and Aches: Elevated cortisol can cause the breakdown of muscle tissue, leading to weakness and body aches.

Lifestyle and Environmental Factors

Sometimes, the cause isn't a medical condition but is instead rooted in daily habits or external influences.

Chronic Stress and Elevated Cortisol

Emotional and physical stress can raise cortisol levels, affecting appetite and metabolism.

Increased Appetite and Fat Storage: Chronic stress can lead to overeating, especially of high-calorie, sugary foods, and promotes the storage of fat, particularly in the abdomen.
Muscle Tension: The body's "fight or flight" response tightens muscles, and if the stress is chronic, this can lead to persistent body aches.

Poor Sleep and Sleep Disorders

Inadequate sleep is often overlooked but profoundly impacts both weight and pain perception.

Hormonal Disruption: Lack of sleep disrupts hunger hormones (increasing ghrelin, decreasing leptin), leading to increased appetite and cravings.
Reduced Physical Activity: Fatigue from poor sleep can decrease motivation for exercise, contributing to weight gain.
Increased Pain Sensitivity: Poor sleep can increase inflammation and lower the pain threshold, making existing body aches feel worse.

Medications as a Cause

Certain medications can have weight gain and body aches as side effects. Common culprits include:

Corticosteroids: Such as prednisone, used for inflammation.
Antidepressants: Especially SSRIs like Paxil, can cause weight gain.
Diabetes Medications: Insulin and sulfonylureas can lead to weight gain.
Other Drugs: Some mood stabilizers, beta-blockers, and antihistamines are also known to cause weight gain.

Chronic Conditions and Inflammatory Responses

Some conditions are characterized by both widespread pain and weight fluctuations.

Fibromyalgia vs. Chronic Fatigue Syndrome (CFS)

These two conditions have overlapping symptoms but distinct primary characteristics. While fatigue is a factor in both, it is the defining symptom of CFS, whereas widespread pain is the signature of fibromyalgia.


Feature	Fibromyalgia	Chronic Fatigue Syndrome (ME/CFS)
Primary Symptom	Widespread pain	Extreme, post-exertional fatigue
Associated Symptoms	Fatigue, brain fog, sleep issues	Muscle/joint pain, trouble concentrating, unrefreshing sleep
Weight Gain	Possible due to inactivity	Possible due to reduced activity and metabolic issues
Unique Feature	Tender points, burning pain	Post-exertional malaise (worsening of symptoms after physical/mental effort)

Osteoarthritis

As the most common form of arthritis, osteoarthritis (OA) involves the breakdown of cartilage in the joints. This causes pain and stiffness, which often leads to reduced mobility and a sedentary lifestyle.

Weight Gain: The pain and limited movement associated with OA can lead to decreased physical activity, resulting in weight gain.
Increased Joint Stress: The weight gain, in turn, puts more pressure on the joints, worsening the OA symptoms and creating a vicious cycle.

Nutritional Deficiencies

A lack of certain vitamins can manifest as body aches and may also be linked to weight gain. Vitamin D deficiency is a key example.

Muscle Aches: Vitamin D is crucial for muscle function, and a deficiency can cause muscle aches, weakness, and bone pain.
Weight Gain: Studies show a correlation between low vitamin D levels and increased body mass. Vitamin D is stored in fat cells, potentially leading to lower levels in the bloodstream of individuals with obesity.

When to Seek Medical Advice

If you are experiencing persistent or worsening body aches and weight gain, it's essential to consult a healthcare provider for a proper diagnosis.

Be specific about your symptoms: Note when they started, their severity, and any other accompanying issues like fatigue, mood changes, or sleep problems. This helps your doctor narrow down potential causes.
Provide a complete medical history: Be sure to mention any family history of thyroid issues, autoimmune conditions, or hormonal disorders.
List all medications and supplements: This includes over-the-counter and prescription drugs, as some can contribute to these symptoms.
Discuss your lifestyle: Mention your typical diet, exercise habits, stress levels, and sleep patterns, as these are critical pieces of the puzzle.

Conclusion

Body aches and weight gain are more than just bothersome symptoms; they are signals from your body that something is amiss. From hormonal imbalances to chronic stress and nutritional deficiencies, the underlying causes are complex and interconnected. While lifestyle adjustments can help, it is crucial to seek a professional medical diagnosis to identify the root cause and develop an effective treatment plan. Ignoring these symptoms can lead to a worsening of the underlying condition and a decline in your overall quality of life. The connection between chronic fatigue syndrome (ME/CFS) and body aches and weight changes is a prime example of how these symptoms are often intertwined Chronic Fatigue Syndrome - Mayo Clinic. Consulting a doctor is the most reliable way to unravel the mystery and find a path toward better health.

Frequently Asked Questions

Yes, hypothyroidism is a common cause of both symptoms. The condition slows down your metabolism, leading to weight gain, and can also cause nonspecific muscle and joint pain, weakness, and stiffness due to low thyroid hormone levels.

Chronic stress elevates cortisol, the stress hormone, which increases appetite and promotes fat storage. High cortisol also leads to muscle tension and can increase pain sensitivity, linking stress to both body aches and weight gain.

Fibromyalgia is characterized by widespread body pain and stiffness. While not the primary symptom, fatigue and decreased activity are common, which can contribute to weight gain.

Poor sleep disrupts hormones that regulate appetite, increases inflammation, and can raise cortisol levels. This contributes to weight gain and increases pain sensitivity, making body aches feel more pronounced.

Yes. Medications such as corticosteroids (like prednisone), some antidepressants, and certain diabetes drugs can cause weight gain and may also have muscle-related side effects.

Low levels of vitamin D are linked to muscle aches, bone pain, and fatigue. Some studies also show an association between vitamin D deficiency and weight gain, especially in people with higher body fat.

You should see a doctor if your symptoms are persistent, worsening, or significantly impacting your daily life. It's important to rule out or diagnose underlying medical conditions like hypothyroidism, PCOS, or others, especially if symptoms are accompanied by extreme fatigue.