10 Science-Backed Reasons Behind Weight Gain (No. 5 is a Surprise)

How many times have we questioned ourselves as to how do I put on so much of weight? I eat less compared to my friend but how does she remain skinny and I don’t?

I am having green tea and xyz supplements but why doesn’t my tummy fat disappear?

And you must have scanned the internet for every bit of information on this but in vain.

Well here are a few reasons which could explain why your weighing scales are tipping on the higher end.

10 Science-Backed Reasons behind Weight Gain

A little insight on these should definitely help you learn the cause and take some preventive action.

1. Imbalanced diet

Well, there is no cheating about this; our food choices affect our body weight.

How many of us do ever strive to consume a healthy diet? How many of us do even know what a healthy diet is?

Current choices are shifting towards a meal that is rich in saturated fats and high in calories.

When it comes to fats and oils, people now are consuming the ‘unhealthy’ fats- saturated fats and omega-6 fatty acids.

Vegetarians especially consume less of the healthy omega 3 fatty acids which are present in fish oil.

This is tipping the scales towards the wrong end.

High dietary protein intake especially animal protein which when used to replace carbohydrates and fats is associated with increased risk of weight gain in future.

There is an increasing trend of consuming fast food over nutritious meals.
Fast food consumption and soda consumption is linked to severe obesity.

It’s not only eating in excess, but even dieting is also linked with future risk of weight gain.

You may be eating fresh fruits and vegetables but if your cooking oil supplies you with more than necessary saturated fatty acids then it is of no use. It is also essential to count your calories.

Excess calories are deposited as fat. Fats have 9 calories per gram while carbohydrates and proteins provide 4 calories per gram.

Large portion sizes available at restaurants provoke you to eat more. So keep an eye on those calories.

2. Genetics & Ethnicity

We all have that one skinny friend who never seems to gain weight and we despise him for his or her genes.

Apart from the environmental factors at play, genetic factors also control one’s tendency to gain weight.

And these genetic factors are not limited to a particular family but it is prevalent in most people belonging to the same race.

There is some evidence available that obesity can be inherited. As per terms used in the field of genetics, there are 3 types:

Melanocortin 4 receptor coded by MC4R gene is the commonest cause of monogenic obesity.

Mutations in this gene accounts for 1-2% of the people who have high BMI and an increased tendency of weight gain.

This protein associated with this gene acts as an appetite suppressor and deficiency or mutation of this gene could contribute to obesity. In fact, binge eating is considered a characteristic of people having mutations in this gene.

Another important gene is ob gene.

This gene favors production of leptin a hormone that signals your brain to reduce food intake and burn calories. Mutations in this gene disrupt leptin production leading to weight gain.

Scientists are attempting to identify various genes linked with obesity with the aim of treating it.

Hey, but you can’t use this as an excuse for those extra pounds.

3. Sedentary lifestyle and lack of exercise

Those who do not exercise are considered to have a sedentary lifestyle.

Compared to our parents and grandparents, we tend to spend most of our time sitting because of our desk job or to watch TV or even while driving.

A study shows that high sedentary lifestyle can bring about a 2.0 increase in BMI in Indian women.

Apparently, over a 4 year period, those commuting by car have a higher tendency to put on weight compared to those who don’t.

Studies clearly establish the link between obesity and professions that add to a sedentary lifestyle along with the prevalence of chronic diseases in such professionals.

Sedentary people require less number of calories than active people. So if calorie intake is not monitored one gains weight.

Reduced physical activity leads to reduced energy expenditure and increased fat accumulation.

And unfortunately, the hazard does not stop there.

Research says that increased fat depot is accompanied by infiltration of immune cells and pro-inflammatory cells which leads to the development of health risks.

In fact, a sedentary lifestyle can increase your risk to develop insulin resistance and this imbalance in glucose metabolism can lead to weight gain.

Non-sedentary activity is associated with a decrease in metabolic syndrome, cholesterol levels, and insulin resistance.

30-45 minutes of moderate physical activity 3-5 days a week can take care of this weight gain cause.

4. Food addiction & unhealthy eating habits

There are some who eat to live and then there are those who live just to eat.

If you find yourself gorging over food, I mean not so nutritious food and feeling guilty about it and then making a rule not to do so in future and still breaking it, then yes you are a food addict!

Data suggests that hyperpalatable or highly processed foods are a trigger factor for food addiction.

Apparently, there is even a scale defined to identify the intensity and type of food addiction.

Endocannabinoids and dopamine are neuromodulators or chemicals secreted by the brain which increase a pleasure related behaviour on food intake especially in case of sugary foods.

Endocannabinoids are appetite stimulating and induce a food seeking behaviour.

Bad eating habits include eating at irregular times, eating out frequently, emotional eating, eating fast food or even skipping meals.

Study proves that emotional eating- eating because you are bored, stressed or fed up, is a significant cause of bad eating behaviours.

Organs such as stomach, intestine and pancreas follow a circadian clock- that is a day and night cycle and this regulates development of fat tissue.

Research shows that individuals who ate a high calorie diet at breakfast lost more weight than those consuming a high calorie diet at dinner.

So definitely food timing is linked with obesity.

Eating rapidly is associated with weight gain.

What we are typically trying to say here is that your food addiction and eating habits are to some extent linked with your brain responses and these if not controlled can lead to serious weight gain.

Reasons Behind Weight Gain

5. Impaired gut health

Gut microbiota are a group of microorganisms present in the intestine that improve digestion and form the first line of defense against toxins entering the body.

The kind of food you eat influences the health of these microbes.

For example high fat diet disturbs the intestinal microflora leading to obesity.

These microbes play an important role in regulating energy harvest, energy expenditure and fat storage thereby influencing development or maintenance of an obese state.

Alteration in such bacterial population can lead to inflammation and onset of obesity associated diseases.

Use of prebiotics and probiotics can replenish a healthy gut microbiota thus promoting better metabolism.

6. Medical conditions

Obesity can occur as a symptom of different disorders such as:

Cushing’s syndrome: A disorder characterized by increased production of cortisol, a hormone produced by adrenal glands. It leads to accumulation of fats around the face which is the characteristic moon-shaped face.

Prader –willi syndrome: It is a genetic disorder and one of its symptoms include uncontrolled appetite leading to obesity.

Poly cystic ovary syndrome: The disorder consists of the development of cysts in the ovary. Hormonal balance is disrupted leading to accumulation of fat in the abdomen.

Diabetes: Insulin resistance is a hallmark of diabetes and this can disturb glucose metabolism leading to weight gain.

Pregnancy and menopause are also associated with weight gain. Around 15% of the women gain 20 pounds or more with each pregnancy. Eating disorders can also contribute to weight gain.

7. Medications

When we talk about drug-induced obesity, the first to top the list are psychiatric drugs.

Antidepressants, antipsychotics and mood stabilizers are few of the drugs that lead to weight gain by interfering in the activity of brain chemicals such as serotonin which regulate appetite.

Also, their sedative effect reduces energy expenditure.

Other drugs that tend to cause weight gain are anti-diabetic medicines, anti-hypertensives, steroids, oral contraceptives etc.

Most of these medicines influence hormonal activity which in turn leads to a fat deposit.

8. Aging

Aging is a common cause of weight gain.

Hypothalamus is a part of the brain that is involved in regulating body weight and energy balance.

Brain cells belonging to this part are influenced by leptin which decreases food intake and promotes burning of calories.

Increased levels of leptin can develop into leptin resistance where the neurons are no longer sensitive to its action and this leads to fat accumulation.

This occurs commonly during aging.

SIRT1 is a protein that controls insulin and leptin resistance and this protein decreases with age implying the reason for weight gain as a result of aging.

Aging and obesity together interact to promote cognitive decline and development of metabolic diseases.

9. Stress

Chronic life stress is casually linked with a greater preference for energy and nutrient dense foods leading to weight gain.

Depending on the severity of stress, undereating or overeating behaviors develop.

In most of the cases, when hit with severe stress you tend to crave for foods high in fats or sugars or extremely palatable food because you are actually craving for pleasure.

Ghrelin is a hormone that stimulates hunger.

This hormone is also linked to stress and emotional eating as it gives you a feeling of pleasure or reward when you consume alcohol or tasty food.

Interaction of other chemicals produced by the brain and ghrelin together can lead to stress-induced weight gain.

However, this feature is not limited to adults but also adolescents. A study demonstrated that stress-related eating behavior is more common in girls than boys.

With such behaviour, girls tend to have more of chocolates, sodas, sweets, and alcohols while boys crave for hamburgers, pizzas, sausages in addition to these items.

If not nipped in the bud, this behavior increases the risk of being overweight or developing eating disorders.

10. Lifestyle

There a number of factors pertaining to the modern lifestyle which contribute to weight gain such as lack of sleep, high-stress levels, lack of discipline, eating too quickly, easy access to nutrient-dense foods etc.

These slowly exert a cumulative action on fat accumulation which brings about changes in your body that resist weight loss.

Lack of sleep is linked with weight gain, especially in children.

Lack of sleep and poor sleep quality lead to increased snacking and various reasons for this have been proposed: increased time for eating, mental stress, imbalance of appetite hormones, more energy required to stay awake etc.

Smoking is another worrisome but preventable factor.

Smoking is linked with abdominal obesity. Women can’t quit smoking because of the fear of weight gain.

Nicotine reduces appetite and energy intake. Therefore when you stop smoking you tend to eat more and gain weight. Also, smoking disturbs insulin and glucose levels.

However, a controlled diet can avoid such weight gain.

Similarly, alcohol consumption is also considered a risk factor for weight gain.


Those of you who keep wondering ‘why do I gain weight’ definitely fall into one of these categories.

But no worries! Once you have identified the cause, its time you found out the solution.

And we are here to help you with that.

Do keep browsing our website for some healthy solutions for weight loss and don’t forget these remedies work only with a low-calorie diet. Eat healthily and have an amazing life!

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