Weight Management 5 MIN READ 52 VIEWS November 23, 2022

Science Behind Why Some People Don’t Gain Weight

Written By HealthKart
Medically Reviewed By Dr. Aarti Nehra

Why some people don't gain weight
Reasons Why Some People Don’t Gain Weight
Why Maintaining Healthy Weight is Important?
Effective Weight Gain Strategies
Healthy Foods to Gain Weight
Foods to Avoid in a Healthy Weight Gain Diet

Mindful eating and regular workouts are important to maintain a healthy weight. We burn calories when we work out. And what we do not burn gets stored as fats, leading to weight gain. But not everyone fits into this mechanism. Ever wondered why some people don’t gain weight despite hogging on unhealthy foods and staying away from exercise? While some believe that the secret lies in their metabolism, there’s more to it. Let’s read through to know more.

Reasons Why Some People Don’t Gain Weight

A lucky few can maintain their body weight despite eating anything. While this may appear to be an advantage, the cause dictating a naturally lean body may not be healthy. Listed below are a few possible reasons why some people don’t gain weight.

1. Fast Metabolism

The rate of metabolism indicates how many calories are burnt at rest. A high metabolism means a person burns more calories at rest and during activity. Therefore, there is no piling up of fats or weight gain. A very high metabolism rate can be unhealthy as the person is unable to maintain a healthy weight.

2. Hyperthyroidism

Hyperthyroidism, or overactive thyroid, is a condition marked by increased thyroid production in the body. The increased levels of the hormone speed up the rate of metabolism. Thus, people with hyperthyroidism have a fast metabolism which leads to faster burning of calories throughout the day.

3. Type 1 Diabetes

Type 1 Diabetes is an autoimmune disorder. As the body begins to target the cells in the pancreas, the production of insulin in the body is disturbed. Lack of insulin causes high levels of blood glucose to be excreted in the urine. Body cells can not utilise glucose as a source of energy and instead burn fat/muscle which leads to unintentional weight loss.

4. Inflammatory Bowel Disease

Inflammatory Bowel Disease is an umbrella term for conditions that affect the intestines. Chronic inflammation in the intestines can result in frequent diarrhoea, leading to excessive weight loss.

5. Eating Disorder

Eating disorders like anorexia nervosa which limit the intake of food, make it hard to maintain a healthy weight. In extreme forms, the conditions completely impair the ability to gain weight.

6. Medical Conditions and Effects of Their Treatment

Certain medical conditions and their treatments can trigger appetite loss, nausea, persistent vomiting, and diarrhoea. These can trigger weight loss and also make gaining weight troublesome and difficult.

7. Genetics

The metabolic rate is unique for every individual. People who genetically have a faster metabolism do not gain weight easily.

Why Maintaining Healthy Weight is Important?

Being overweight or obese is a damaging health condition. It increases your risk of developing serious health conditions like heart disease, type 2 diabetes, and certain cancers. But not being able to gain a healthy weight is an equally devastating health condition. People with lower than normal Body Mass Index (BMI) have acute deficiencies, making them susceptible to various health conditions. The demerits of being underweight include:

1. Skin and hair problems

Lack of adequate nutrients in underweight people causes thinning and drying of hair and skin.

2. Gradual Bone Loss

People with low BMI have reduced bone mineral density. This increases the risk of fractures.

3. Reduced Immunity

Since people with low BMI have acute nutrient deficiencies, the production of white blood cells gets impaired. White blood cells are important to build the body’s immunity or the natural defence mechanism.

4. Increased Risk of Heart Ailments

Potassium, calcium, and sodium are minerals important for maintaining a healthy heartbeat. Low BMI caused by malnutrition affects normal heart rhythm.

5. Iron Deficiency

Underweight people are iron deficient. The lack of iron in the blood lowers the red blood cell count, leading to anaemia. This causes persistent fatigue, dizziness, and frequent headaches.

6. Irregular Menstrual Cycle

A healthy BMI is important in order to ensure a regular menstrual cycle. Underweight women experience irregular, delayed, or no periods. This increases the risk of infertility.

7. Pregnancy Complications

Pregnant women with low BMI are more likely to go into preterm labour. This increases pregnancy complications.

8. Post-Surgery Complications

People with low BMI are at a higher risk of post-surgery complications because of reduced immunity.

Effective Weight Gain Strategies

Having a normal BMI is the best thing for health. Interestingly, while adding weight is considered easier than losing weight, some people still find it difficult to gain weight. The best way to gain weight is through lifestyle changes. Listed below are a few changes that improve your chances of gaining a healthy weight. These are:

1. Add Up on Calories

Consuming calories more than what you expend during the day is the key to weight gain. Try consuming at least 500 more calories per day than what your body requires.

2. Follow a Weight Gain Diet Plan

Whole grains and healthy fats are the best foods to gain weight. A weight gain diet plan will leave you caloric surplus. It is important that you get your calories from healthy foods to gain weight.

3. Concentrate on Muscle Building

Weight training is a must for building muscles. As muscles weigh more than fat, indulging in weight training is the best way to gain some kilos in a healthy manner.

4. Increase Eating Frequency

Eating meals frequently will allow you to pack more calories throughout the day. Also, breaking bigger meals into smaller ones will keep you energetic for the whole day which will provide you with the power to work out longer and harder.

5. Increase Portion Size

Simply eating a little extra in every meal will help you add calories easily and faster. When you decide to increase the portion size, ensure that you add on high-calorie weight gain foods.

6. Supplements and Shakes

Protein shakes and supplements are an easy way to pack extra calories into your daily diet. Drink full-fat milk and blend it with your favourite high-calorie fruits.

7. Do Not Fill It Up with Water

Avoid drinking fluids before meals. This curbs appetite. Instead, drink water at least half an hour after your meal. You can sip on a high-calorie milk-based drink with a meal. But avoid sodas.

8. Make Every Bite Count

Include nuts, dry fruits, and high-calorie healthy snacks in your bite. Whenever you feel like munching, grab onto high-calorie foods. Use high-calorie salad dressing and topping to garnish your dishes.

9. Regular Exercise

Exercise will burn calories. But it also stimulates appetite. Furthermore, weight training exercises are the best way to increase lean muscle mass which results in healthy weight gain.

Healthy Foods to Gain Weight

Listed below are the best foods to gain weight. They help you add muscle mass and gain weight in a healthy way:

  • Protein smoothies
  • High-calorie fruits
  • Full-fat milk
  • Full-fat yoghurt
  • Rice
  • Nuts
  • Peanut butter
  • Dry fruits
  • Whole grain cereals
  • Red meat
  • Potatoes
  • High starch foods
  • Oily Fish
  • Avocados
  • Protein Supplements
  • Cereal bars
  • Dark chocolate
  • Cheese
  • Whole eggs
  • Healthy oils and fats

Foods to Avoid in a Healthy Weight Gain Diet

Although everything you eat adds to calories. But for a healthy weight gain, the source of calories is important. Listed below are foods one must avoid in a weight gain diet:

  • Sugar-sweetened drinks
  • Carbonated drinks
  • Processed meat
  • Alcohol
  • Fried potato chips
  • Refined flour
  • Saturated fats
  • Artificial sweeteners


We all wonder why some people don’t gain weight. In fact, for some people, gaining weight is just as difficult as losing weight is for others. There are several reasons behind this. Underlying medical conditions, associated treatment, genetics, etc. all play a crucial role in regulating our metabolism. 
But following a weight gain diet plan and including the best foods to gain weight can help in healthy weight gain. Remember to adopt healthy weight gain strategies to add healthy weight as bulking up on unhealthy foods can fuel other health concerns.

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