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25 Sneaky Reasons You're Gaining Weight When You're Doing Everything Right

Find out which common habits may be to blame for your weight gain and what you can do about it.
FACT CHECKED BY Alexa Mellardo

If the number on the scale keeps creeping up despite your best efforts, you're not alone. A OnePoll survey revealed that a staggering 95% of Americans tried to shed excess weight within a five-year timeframe (from 2018 to 2023). Nearly half of the respondents said they struggled with achieving their weight-loss goals (and actually gained weight). If you've found yourself in a rut, don't fret. We spoke with experts who share 25 super sneaky reasons you're gaining weight when you're doing everything right.

Why is it so hard to lose weight and keep it off? To help solve this dilemma, we asked nutrition and weight-loss professionals to weigh in (pun intended) on the most common reasons you're gaining weight when you're seemingly doing all the right things. Read on to discover what they are so you can conquer your weight-loss woes.

You're prioritizing workouts, not other activities.

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While exercise is an invaluable tool for losing weight, you can't expect to reach your weight-loss goals if you work out for 30 to 60 minutes but are sedentary for the remainder of the day.

"Getting enough exercise is vital for overall health, but that means being active outside of workouts," Kate Meier, CPT, a certified personal trainer with Gym Garage Reviews, tells us. "Small actions like taking the stairs at work, walking the dog, or playing with your kids can significantly impact your metabolism and help you lose weight, but they're often overlooked."

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You're underestimating portion sizes.

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According to a study by Cornell University, people of average weight underestimate the number of calories they consume by nearly 20%, while overweight people underestimate it by nearly 40%. So, at the end of the day, calories are still calories, regardless of whether you eat healthy food. That's why paying close attention to portion sizes is essential when your health goal is weight management.

"Even if you're eating healthy foods, overeating may mean you're consuming too many calories," says Trista Best, RD, a registered dietitian with Balance One Supplements.

You're not adjusting your nutrition as you progress.

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A lesser-known fact about weight loss is that your body's needs and metabolism change after losing weight, according to research. To put it into context, a 110-pound person requires much fewer calories than a 220-pound person. That's because the smaller your body, the less energy it requires.

"As you lose weight, your body's caloric needs will change. So if you've noticed a lack of progress or weight gain after consistent weight loss, not readjusting your nutrition may be the culprit," explains Meier.

You're consuming too many calories through beverages.

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Another one of the top reasons you're gaining weight is you're unknowingly consuming too many calories through beverages. Soda, juice, wine, beer, lattes. These beloved beverages, though enjoyable, are loaded with empty calories that provide very little nutritional value. If you're eating in a calorie deficit or to maintain weight but regularly consume these high-calorie beverages, you could be counteracting your weight-loss efforts.

"Liquid calories from sodas, juices, and alcohol can add up quickly and contribute to weight gain. Stick with water or low to zero-calorie beverages and save your calories for nutrient-dense foods instead," says Best.

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You're not sleeping enough.

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Getting enough quality sleep is a critical aspect of any healthy weight loss plan, says the Sleep Foundation. In addition, research shows that lack of sleep while dieting can negatively affect weight loss and lead to overeating by increasing the production of ghrelin (the "hunger hormone").

"Sleep is essential for losing weight for various reasons, but it's easy to fall off track with this aspect of your fitness routine. Adults should aim to get about seven or more hours of sleep per night, and that sleep would ideally be uninterrupted," says Meier.

You're not getting enough protein.

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Among the three macronutrients—carbohydrates, protein, and fats—protein is the most satiating, meaning it makes you feel full faster and longer. Research shows that high-protein diets can reduce body weight and help prevent overeating.

"Whether it's from plant or animal sources, try to have a serving of protein at each meal or as a snack to increase satiety and prevent overeating," says Best.

You're gaining muscle.

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Did you know that gaining muscle could be a major reason you're gaining weight? Muscle is denser than fat, according to research. So, if you've been hitting the weights and doing regular resistance training, odds are, you're not losing weight due to muscle gains.

"If you've truly been dedicated to a fitness plan and find that you're starting to gain weight, there's a chance you're actually gaining muscle," Meier. "If you look like you're still getting fitter and notice slight differences, like your clothes fitting differently, but the scale shows a higher number, this is likely the case."

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You're stressed out.

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One study reveals that learning to chill out can actually aid in weight loss.

"High stress levels can trigger the release of cortisol (the stress hormone), which can increase appetite and lead to overeating," Best explains. "Find a stress reduction method that works for you, or evaluate areas of stress that can be removed or reduced."

You're on medication that causes weight gain.

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Many popular medications may have side effects such as weight gain. "However, this doesn't mean you should stop your medications, especially these types, but speak to your prescribing healthcare provider for ways to counteract this side effect," Best notes.

Your hormones are out of balance.

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Hormonal imbalances may be the culprit behind your weight loss woes. According to the Mayo Clinic, several hormones can affect how your body indicates that it requires food and uses energy. Too much cortisol and a low amount of thyroid hormones, for instance, can result in unintentional weight gain.

"Conditions such as polycystic ovary syndrome (PCOS) and thyroid disorders can cause weight gain," says Best. "Have thorough blood tests done annually or bi-annually to evaluate your hormone status and areas that could use improvement or balance."

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Your muscles are inflamed.

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Research shows that inflammation is the root cause of many common diseases. Additionally, inflammation can make it more challenging to lose weight and easier to pack on extra pounds by heightening your risk of type 2 diabetes.

"When a particularly intense or new type of workout taxes your muscles, this can cause inflammation in tandem with delayed-onset muscle soreness, which can lead to some water weight gain as you recover," states Meier.

You're not getting enough physical activity.

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It should go without saying, but you're unlikely to shed pounds if you're not moving your body enough and expending energy.

"Even if you're eating well, if you're not moving your body enough, you may still gain weight," says Best. "Physical activity can also greatly reduce stress and provide you with feel-good hormones."

You're weighing yourself at a bad time.

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Typically, your weight is at its lowest point in the morning after you get out of bed and go to the bathroom. It gradually rises throughout the rest of the day as you eat and drink. That's why it's critical to step on the scale at the same time daily.

"It's normal for weight to fluctuate, and a typical adult's weight can fluctuate by about five pounds in a single day," says Meier. "If you see the number on the scale going down for the most part, outlier weights may be chalked up to daily fluctuation. To better grasp your weight fluctuation, weigh yourself around the same time each day."

Your workouts have become stale.

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You know it's time to switch up workouts when you've become bored and no longer feel tired afterward.

"If you do the same exercises repeatedly without any changes, your body adapts to them, and they may not be as effective," Meier stresses. "Instead, try switching up your workouts or routine every few weeks to stimulate your muscles differently."

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You're skipping meals.

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You may think you're doing yourself a favor by skipping breakfast, lunch, or dinner, but delaying your hunger can cause overeating and weight gain. For example, a 2021 study published in Nutrients found that not eating dinner was linked to obesity and being overweight.

"Skipping meals can lead to overeating later on and can also slow your metabolism," explains Best. "You're also more likely to overeat at the following meal due to the excessive hunger you're likely experiencing."

You have a medical condition you're unaware of.

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If you have an underlying health condition you don't know about, you may have more difficulty keeping weight off. Conditions such as sleep apnea, hypothyroidism, and depression can hinder weight loss and cause weight gain, according to WebMD.

"Many medical conditions are associated with weight gain, so it's important to visit your doctor if your weight changes significantly without any lifestyle changes," recommends Meier.

You're eating too quickly.

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In our lightning-paced world, it's easy to fall into the trap of checking items off our to-do lists without paying attention to what we're actually doing. So, instead of scarfing down your next meal, practice mindful eating by eating slowly while paying close attention to your body's hunger signals.

"Eating too quickly can lead to overeating because your brain doesn't have enough time to register that you're full," says Best.

Your diet is too restrictive.

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Multiple studies show that restrictive diets ultimately hinder weight loss and instead contribute to weight gain.

"When you go on highly restrictive diets, your body may be unable to handle coming off the diet. For example, individuals who go from a super low-carb diet to a regular balanced diet may gain a substantial amount of weight right out of the gate," explains Meier. "Slow, steady, and balanced diets are the better route for sustainable weight loss."

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You're eating too many processed foods.

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Another one of the sneaky reasons you're gaining weight? Indulging in processed foods! In general, processed foods have a high calorie count, sugar, sodium, preservatives, unhealthy fats, and no nutrients. This makes processed foods easy to overconsume and could be a reason why you're packing on extra weight.

"Processed foods often contain added sugars, fats, and salt, which can contribute to weight gain," says Best.

You're retaining water.

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"Water weight is one of the factors that go into daily weight fluctuation, and being hydrated or dehydrated can lead to substantial losses or gains in a day," explains Meier. "Even when you lose weight quickly in a few days, much of it is often water. Dehydration can lead to short-term water retention, but long-term water retention can be associated with health issues and warrants a doctor's visit."

You're getting older.

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"As you age, your metabolism slows down, making it easier to gain weight. Speak to your healthcare provider or registered dietitian for tips on counteracting this side effect," Best advises.

A primary reason weight loss is more challenging as you get older is that you naturally lose lean muscle. Muscle torches more calories than fat.

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Your genetics make it harder to lose weight.

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Your genetics can impact your weight in several ways. For example, genes can affect metabolism, satiety, appetite, cravings, body-fat distribution, and the habit of eating as a stress-coping mechanism.

"Your genes can play a role in your body shape and how easily you gain weight. While you can't change your genetics, understanding the cause can help reduce frustration," says Best.

You're not eating enough fiber.

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Fiber is an essential nutrient for healthy weight loss. For example, one study found that dietary fiber intake can promote weight loss and diet adherence in overweight and obese adults.

In addition to helping you feel full, consuming high-fiber foods slows down the digestion process and helps prevent blood sugar spiking. This allows you to better manage your insulin and blood sugar response to food.

You don't get dressings or sauces on the side.

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Whether you're enjoying a meal out or eating a delicious homemade sauce, it's a good idea to ask for your dressing or sauce on the side. Unfortunately, many dressings and sauces (especially store-bought ones) are loaded with empty calories, added sugars, saturated fat, and oils that can drastically increase the calorie content of your meal without you even realizing it.

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You're not fasting long enough.

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If you've listened to any health-related podcasts in the last few years, you've likely heard of intermittent fasting and its weight-loss benefits. Intermittent fasting involves cycling between periods of eating and fasting.

For instance, you may decide to eat as you normally do but restrict that eating time to a specific eight-hour window daily. In that case, you might not have breakfast, eat lunch at 12 p.m., and savor dinner by 8 p.m. There's also "alternate-day fasting," which is a form of intermittent fasting that calls for following your typical diet one day and then fasting or consuming a tiny meal that's fewer than 500 calories the following day.

Adam Meyer, RHN
Adam is a health writer, certified holistic nutritionist, and 100% plant-based athlete. Read more about Adam
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