What To Do If You Experience Sudden Weight Gain? (+ 7 Key Strategies)

Why am I gaining weight so fast all of a sudden?

There are numerous reasons why you might experience sudden weight gain, particularly in your stomach and thighs, commonly known as “belly weight gain.” Some of the most common causes might include:

1. Genetics and body type

Research suggests genes account for 40% of the predisposition to be overweight in some people, while for others, it’s as high as 70%.3

Some may notice fat accumulation in specific areas like the abdomen, hips, or thighs, largely due to genetic factors inherited from their parents. Hence, genetics might significantly influence how and where our bodies store fat, contributing to the diversity of body types.3

2. Age-related changes

As we journey through life, it’s important to understand that age-related changes in our bodies are completely natural, and one such change is the gradual slowing of metabolism. This means that as we age, our body’s ability to burn calories decreases, which can lead to weight gain, especially around the midsection or belly.4

3. Hormonal imbalances

Hormonal imbalances can be a pivotal factor in weight gain, particularly during significant life stages such as menopause, pregnancy, or changes in hormonal birth control.6 During these times, the body’s natural hormone levels fluctuate, which can disrupt metabolism and lead to unexpected weight changes. For example:

• Menopause: During this stage, declining oestrogen levels may slow down metabolism and lead to increased fat storage around the abdomen.4
• Pregnancy: It introduces a complex interplay of hormones that support foetal development but might also contribute to weight retention post-birth.5

4. Medications

Certain medications can cause weight gain as a side effect. For instance, antidepressants, corticosteroids, and some diabetes medications are known to potentially cause an increase in weight.6

5. Thyroid disorders

Thyroid issues, such as hypothyroidism, can significantly impact your metabolism, making it challenging to maintain a healthy weight despite conscious efforts. When the thyroid underperforms (underactive thyroid), it may not produce enough hormones to regulate metabolism, which might result in weight gain.7

6. Fluid retention

Fluid retention, or edema, is when the body holds excess water. Excess fluid retention might cause swelling in the ankles or abdomen and lead to unexpected weight gain.8,9  

This condition can be caused by heart failure, kidney disease, liver dysfunction, or excessive sodium intake. Additionally, certain medications like steroids or nonsteroidal anti-inflammatory drugs (NSAIDs) might contribute to this issue.8,9

7. Lifestyle changes

Sudden lifestyle changes, particularly in areas such as diet, physical activity levels, or sleep patterns, can significantly impact your health and lead to rapid weight gain. For instance:

• Diet: Abrupt changes to your diet, like consuming more high-calorie foods or drastically reducing nutrients, can disrupt your metabolism and cause unwanted weight gain.12
• Physical activity: A sudden decrease in physical activity can reduce daily calorie burn, leading to an energy imbalance and weight gain.13
• Sleep: Inadequate or irregular sleep (insomnia) patterns can affect hormones that regulate hunger and appetite, making it challenging to maintain a healthy weight.10
• Stress: High stress level elevates cortisol levels, leading to weight gain, especially around the abdomen. Cortisol is known to trigger cravings for high-calorie foods and alter fat storage.11

If you’re wondering, “Why am I suddenly gaining weight in my stomach and thighs?” consider one or more of the potential causes mentioned above. For any health concerns, book an appointment with your Aussie-based doctor or nurse practitioner today for personalised guidance.

Why am I gaining weight so fast when I barely eat?

If you’re experiencing weight gain despite eating very little, it can be particularly frustrating. In addition to the previously mentioned causes, you might also consider these potential factors:

1. Undiagnosed medical conditions

Conditions such as Cushing’s syndrome or polycystic ovary syndrome (PCOS) can cause weight gain despite low calorie intake. Cushing’s syndrome involves an excess production of cortisol, which can lead to fat accumulation and other metabolic changes.14 Similarly, PCOS affects hormone levels in women and may disrupt normal metabolism and fat storage processes.15

2. Slow metabolism due to extreme calorie restriction

Severely restricting calories may  trigger “starvation mode,” where the body slows metabolism to conserve energy. A slower metabolism might likely burn fewer calories at rest, making weight loss harder and causing fatigue.This response protects the body during perceived scarcity, helping it function with limited resources.16 

What illness makes you gain weight?

Several medical conditions can contribute to sudden weight gain:17

• Hypothyroidism: An underactive thyroid gland can slow down metabolism, leading to weight gain.
• Polycystic ovary syndrome (PCOS): This hormonal disorder can cause weight gain, particularly around the midsection.
• Cushing’s syndrome: This condition results from excessive cortisol production and can cause rapid weight gain, especially in the face, neck, and trunk.
• Insulin resistance or diabetes: When cells become resistant to insulin, it can lead to weight gain and difficulty losing weight.
• Certain psychiatric medications: Some antidepressants and antipsychotic medications can cause significant weight gain.
• Sleep apnea: This sleep disorder can disrupt hormones that regulate hunger and fullness, potentially leading to weight gain.
• Congestive heart failure: This condition can cause fluid retention, leading to sudden weight gain.

If you suspect an underlying medical condition is causing your weight gain, consider consulting with your healthcare provider for diagnosis and treatment.