Eating less and still gaining weight? Doctors explain the hidden reasons

Experts explain how under-eating, skipped meals, hormonal imbalance, stress and metabolic slowdown can push the body into survival mode and make losing weight harder over time

For many people struggling with weight gain, the frustration is not about overeating but about eating less and still seeing the scales creep up. Skipped meals, tiny portions and repeated dieting often feel like the right approach to weight loss, yet the body does not always respond the way we expect.

 

Doctors say weight regulation is far more complex than simple calorie counting, because metabolism, hormones, lifestyle and everyday stress quietly shape how the body stores fat.

 

Why eating less can slow the body’s metabolism

 

According to Dr Tarun Mittal, Vice-Chairperson, Laparoscopic and Robotic Bariatric Surgeon at Sir Ganga Ram Hospital, Delhi, the body adapts quickly to food restriction. When people consistently under-eat or skip meals, metabolism slows so that energy can be preserved, and fewer calories are burned even at rest.

 

“Loss of muscle mass during under-eating further reduces metabolism, making weight gain possible despite low food intake,” Dr Mittal explains. Stress, poor sleep and hormonal changes add to this imbalance, which is why even small meals can end up being stored as fat.

 

Dr Rakesh Durkhure, Head – General, MI and Bariatric Surgery at Artemis Hospitals, adds that skipping meals also affects hunger hormones. “The body learns to store fat as a way to survive over time,” he says, noting that hunger hormones often rise later in the day, quietly pushing people towards overeating without realising it.

 

Why crash dieting and repeated calorie cuts backfire

 

Repeated crash dieting signals to the body that food is scarce. In response, it shifts into conservation mode, slowing metabolism to preserve energy. Basal metabolic rate, or BMR, is the number of calories the body burns at rest to maintain vital functions, and when it drops, fewer calories are burned even without an increase in food intake.

 

Over time, this metabolic slowdown is accompanied by muscle loss and a greater tendency to store fat, a process known as metabolic adaptation. This explains why weight-loss plateaus and rebound weight gain are so common.

 

“The body learns how to function on fewer calories,” says Dr Durkhure, adding that returning to normal eating later can then lead to fat gain rather than weight loss.

 

Medical conditions that make weight harder to control

 

Some health conditions directly affect how the body uses energy. Insulin resistance, for instance, prevents cells from responding properly to insulin, so glucose remains in the bloodstream and excess insulin pushes the body to store fat.

 

Hormonal disorders such as polycystic ovary syndrome (PCOS) disrupt appetite regulation and fat storage, while thyroid conditions also play a major role. Hypothyroidism, or low levels of thyroid hormone, slows metabolism and reduces calorie burn, increasing the risk of weight gain. Hyperthyroidism, marked by high thyroid hormone levels, speeds up metabolism and may cause unintended weight loss.

 

“These conditions make it difficult for the body to balance energy use and fat storage,” says Dr Durkhure, explaining why weight loss can remain stubborn even when food intake is low.

 

How ultra-processed foods quietly add to weight gain

 

Many people believe they eat very little but overlook where their calories come from. Ultra-processed foods are calorie-dense, low in fibre and poor at keeping people full. Sugary drinks, sauces, flavoured snacks and ready meals often contain hidden sugars and unhealthy fats that add up quickly.

 

Dr Mittal notes that these foods raise blood sugar rapidly and encourage fat storage, while also triggering frequent snacking. Even small portions can carry a heavy calorie load without offering real nutrition.

 

Why weight gain is not just about calories

 

Calories matter, but they are not the whole story. Several everyday factors influence how the body handles energy:

 

• Chronic stress raises cortisol, which encourages fat storage, especially around the abdomen
• Poor sleep alters hunger hormones, increasing cravings for high-energy foods
• Irregular eating patterns slow metabolism and increase fat storage
• Certain medications, including steroids and some antidepressants, can cause weight gain as a side effect

 

Smarter habits that support healthy weight

 

Instead of extreme restriction, doctors advise focusing on consistency and balance:

 

• Eat regular, balanced meals to support metabolism
• Choose whole, nutrient-dense foods over processed options
• Include protein and fibre in every meal to preserve muscle and improve satiety
• Stay active with a mix of cardio and strength training
• Manage stress through yoga, meditation or relaxation techniques
• Aim for seven to eight hours of quality sleep each night
• Seek medical advice if weight gain persists despite lifestyle changes

 

Weight gain despite eating little is not a failure of willpower. It is often the body responding to stress, hormonal shifts and survival cues. Understanding these hidden drivers can help people move away from extreme dieting and towards habits that tuly support long-term health.     

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This report is for informational purposes only and is not a substitute for professional medical advice.