Have you ever wondered why you are gaining weight, although it seems like you haven't changed your diet or lifestyle? It's not uncommon for people to step on the scale only to see the number they didn't expect, or they realize clothes don't fit them anymore in a way they used to. These problems are common, but they never cease to puzzle us. To help you manage weight more effectively in this post, we are going to provide answers to the "why am I gaining weight so fast” question that’s on your might right now. So, let’s start.

Your diet consists mainly of processed foods 

The reality is that most people don’t eat a healthy diet. We tend to eat a lot of processed foods that have little to no nutritional value and contribute to a rapid weight gain. Processed foods are also high in unhealthy fats and abundant in sugars and preservatives, all of which are bad for your weight. A growing body of evidence confirms that consumption of ultra-processed foods is associated with a higher risk of obesity, metabolic syndrome, hypertension, and high levels of LDL or bad cholesterol (1). A study from February 2019, published in the Canadian Journal of Public Health, found that people who consumed ultra-processed foods were 32% more likely to be obese (2). 

TIP: Consider reducing the intake of heavily processed and refined foods. Instead, you may want to opt for whole foods such as fruits, vegetables, nuts and seeds, fish, and other healthy foods.

You eat quickly

We are always in a hurry to do something as fast as possible and eating is not an exception, for most of us. Let's be honest; all of us are guilty of eating too quickly at one point or another. However, some people may turn eating quickly into a habit without realizing it can lead to weight gain. Studies reveal that eating quickly is positively associated with excess body weight (3). The reason why you can gain weight by eating quickly is that it can take a while for the body to realize it is full. So, when you eat quickly, you unintentionally eat more food than the body needs to feel satiated. 

TIP: Fast eaters may want to slow down when eating their food and chew thoroughly before they swallow. That way, you will avoid overeating and succeed in maintaining a healthy weight.

Your thyroid is slow

The thyroid is a butterfly-shaped gland located low on the front of your neck. Functions of the thyroid and its hormones are numerous, including regulation of metabolism, body temperature, among other things. Thyroid dysfunction is associated with changes in body weight and body composition, body temperature, energy expenditure, regardless of the physical activity levels. Hypothyroidism or underactive thyroid, a common condition indicated by insufficient production of thyroid hormones, reduces thermogenesis, decreases metabolic rate, and is strongly associated with higher BMI and increased prevalence of obesity (4). Therefore, a potential reason behind your surprising weight gain could be an underactive thyroid.

TIP: If you’re gaining weight and not sure how it may be useful to see the doctor and get thyroid hormone levels checked. The simple blood test is all that’s needed. This is particularly important if you also have other symptoms such as weight loss, mood swings, high cholesterol, increased sensitivity to cold.  

You don’t drink enough water

About a fourth of people in the US don’t drink water daily (5), and that's a big problem. The body needs water to function properly. It also needs water for weight management. Unfortunately, most of us wait to feel thirsty in order to drink some water, but by then, the body has already started experiencing some symptoms of dehydration. Thirst can also trick your body into feeling hungry and thereby make you eat more food than the body needs. Then, you gain weight. Drinking water can increase the number of calories you burn, suppress your appetite, and promote weight loss (6). 

TIP: Strive to drink four to eight glasses of water during the day. Make sure you drink “regular” water instead of vitamin and flavored waters that contain hidden sugars. Also, try not to replace water with fruit juices (especially store-bought) as they are also sugar-laden.

You eat late at night

Do you ever feel like eating something late at night? We usually crave for unhealthy foods such as pizza, fries, or candies at late hours. Sometimes the craving can be difficult to resist, so we give in to it. Eating late at night is one of the most common reasons behind fast weight gain. Why? The reason is simple; late eaters tend to eat more calories. Evidence shows that people who eat closer to their bedtime tend to consume more calories overall compared to their counterparts who ate their last meal earlier (7). 

TIP: Try not to eat late at night. It would be ideal to avoid it entirely, but if you simply must eat something, then opt for some healthy, low-calorie snack. One way to avoid eating is to brush your teeth. Food tastes horrible when you've just brushed your teeth, and the craving will probably go away. 

You consume too much sugar

Everybody loves sweets, cakes, desserts, and other foods for their deliciousness. A sweet tooth can pave the way to weight gain and increase your risk of other health problems. Besides sweets and candies, we also tend to consume too much sugar through products such as sports drinks, sodas, store-bought fruit juices, and even some processed foods contain hidden sugars. These foods and beverages are high in calories. If you consume more calories than burn, you gain weight. That’s why sugar is particularly harmful to people with a sedentary lifestyle. 

TIP: The goal is to avoid sugar-laden products and foods entirely but to make it easier, you may want to reduce intake first. There are various healthier alternatives to your favorite sweets, so they may help you avoid sugar itself and processed foods. 

You are a social butterfly

Nope, you are not mistaken – being too social is also a factor behind rapid weight gain. Before you dismiss this, hear us out. You like to hang out with people, go to restaurants, enjoy nice food, or throw dinner parties, Superbowl parties, and whatnot? Hanging out with other people usually involves eating food, and you may end up overeating without even realizing it. This leads us to the previously mentioned fact that weight gain happens when you consume more calories than your body burns.

TIP: Don’t worry, the answer is not to ditch your friends and stop socializing. The point is to be mindful of what and how much you eat when you’re among friends, coworkers, family members, and other people. If you’re not hungry, don’t eat just for the sake of eating. Listen to your body. 

You overeat on healthy foods

One of the biggest mistakes people make regarding healthy foods is the belief that the more, the better. So, when we start eating some healthy, we think the more we eat, the better it is, especially when that food is good for weight management. That's not how it works. Healthy foods are low in calories, but they still have them. So if you eat excessively and don't exercise, you still consume more calories than you burn. When combined with other factors, this can also lead to weight gain.

TIP: Don’t go by the “the more, the better” rule. Eat moderately, even when eating healthy foods. That way, you’ll be full and won’t end up eating too much. 

You have a sedentary lifestyle 

We have become a sedentary society that spends most of its time watching TV or binge-watching Netflix shows and movies while munching on unhealthy snacks. When we have to do something, we usually opt for the fastest and most convenient route just to move less as possible. A sedentary lifestyle slows metabolism and doesn't burn enough calories, which is why we end up gaining more weight than we ever thought we could.

TIP: Sedentary lifestyle is a major factor behind fast weight gain, and the natural solution is to be more active. But, it's important to clarify this doesn't refer to exercise only. Besides regular exercise, you also need to introduce more physical activity in your daily life. For example, instead of the elevator, you can take the stairs. Instead of driving to the store, take a walk. You can also do chores around the house, ride a bicycle to work, options are endless. 

You don’t sleep enough

Sleep deprivation is a common occurrence today. Instead of going to bed at "normal" hours, we spend our nights staring at the phone, laptop, TV, or something else. Lack of sleep harms our health in more ways than one, and it also contributes to weight gain (8). Sleep deprivation can lead to weight gain through multiple mechanisms, including hormonal imbalances, tiredness, and lack of motivation to exercise or do anything but sit and eat. 

TIP: To maintain weight in a healthy range and improve general health, it is crucial to get enough sleep. That means you need to get eight to nine hours of sleep at night. More importantly, it's important to establish a regular sleep schedule. What's that? Make sure your bedtime every night is at the same time and wake up every morning at the same time as well. 

You follow fad diets 

Have you ever tried some popular diet only to realize you actually gained even more weight a few weeks later? That's a common problem, and it perfectly depicts the dangers of fad diets that take the internet by storm. What's the problem here? Some diet programs work while others do not. Bad weight loss diets usually involve severe calorie restriction and require avoidance of certain food groups. Restrictive diets are associated with the uncomfortable yo-yo effect where a person gains even more weight than they initially lost. These diets work for a short period of time, but as soon as you increase food intake, the problem happens.

TIP: Instead of fad diets, restrictive programs, and questionable trends, you should strive to eat a well-balanced diet. Remember, your body needs a wide range of nutrients to function properly. This also means you need to eat different foods as each group delivers specific nutrients. Staying true to a healthy diet that involves a plethora of ingredients is easier and more effective than following some diet fad that will do more harm than good.

You eat in front of the TV

Let's be honest; most of us are guilty of this one. We prepare food and sit in front of the TV to watch something interesting when we eat. Big mistake! As you're deeply focused on TV, you eat more than the body needs and don't even realize it. When this behavior becomes a habit, it can lead to weight gain.

TIP: Try not to watch TV when you're eating. It's important to be mindful when it comes to food, and you can't do that if you are too focused on the screen in front of you.

Other things that cause weight gain

  • Eating from large plates and bowls 
  • Eating in restaurants and fast food places rather than cooking
  • Not eating enough protein and fiber
  • Shopping without a grocery list and when hungry
  • Not eating enough fruits and vegetables
  • Using too much salad dressing
  • Irregular mealtimes


If you’ve ever wondered why am I gaining weight so fast, this post has provided you with tons of reasons that you can use to modify your lifestyle. Maintaining weight in a healthy range requires lifestyle adjustments, but it's an entirely achievable goal. Make sure you eat a healthy diet, drink enough water, exercise regularly, get enough sleep, and avoid fad diets. With a few simple tweaks, you'll notice you're not gaining weight anymore. 


(1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5787353/
(2) https://www.ncbi.nlm.nih.gov/pubmed/30238324
(3) https://www.ncbi.nlm.nih.gov/pubmed/26100137
(4) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911848/
(5) https://www.ars.usda.gov/ARSUserFiles/80400530/pdf/DBrief/7_water_intakes_0508.pdf
(6) https://www.healthline.com/nutrition/drinking-water-helps-with-weight-loss#section1
(7) https://www.ncbi.nlm.nih.gov/pubmed/25439026
(8) https://www.ncbi.nlm.nih.gov/pubmed/23419528

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