Why Can't I Lose Weight?

Written by Kara Mayer Robinson, Marijke Vroomen Durning, RN
Medically Reviewed by Michael Dansinger, MD on July 02, 2025
9 min read

You try hard, but that scale won't budge. It's only human nature to wonder if those pounds will ever come off. But don't give up on your weight loss plan just yet. See if one of these factors might be secretly affecting your ability to lose weight.

Skipping breakfast could be one reason you have trouble losing weight. When you take a pass on that first meal of the day, it can work against you. You're likely to get hungrier later, so you may overdo it at lunch. “We might find ourselves reaching for a larger portion sizes or more calories than we would have if we had set ourselves up for success in the morning,” says Meghan Salamon, a registered dietitian at Massachusetts General Hospital. Ideally, this means eating within two hours of waking up, she explains.

Looking for ideas? A high-fiber, protein-packed breakfast can help you feel full, longer. Try cottage cheese with fruit, eggs with whole-wheat toast, or Greek yogurt with a banana.

A late-night meal can spell trouble for your weight loss plan. It may raise your body temperature, blood sugar, and insulin, which makes it harder for you to burn fat. Not eating too close to bedtime has other benefits, Salamon says. “I like to recommend patients stop eating at least two hours before bed because it improves their sleep. If we eat too close to bedtime, it can interfere with the way that our brain produces melatonin,” she says.

Be careful about snacking after dinner, too. You take in more calories than you realize when you nibble while you watch TV or use the computer. You may also be tempted to eat unhealthy foods like ice cream or potato chips. This is called habitual hunger, Salamon explains, and if you’re watching TV while you’re snacking, you can’t give full attention to your snack or meal, and you can’t gauge the true amount of what you’re eating. 

Stress is a big food trigger for many people, and it can work against you as you try to lose weight. And stress eating usually involves foods that aren’t the healthiest. They’re often high in fat, sugar, and calories. Your body also tends to store more fat when you're stressed

When your body is stressed, it wants to protect you. One of those ways is by making a hormone called cortisol. This hormone tells your body to store more visceral fat, known as belly fat. 

To reduce stress, try exercise or meditation, or distract yourself with hobbies or other activities you enjoy.

Like many health issues, your gender assigned at birth could make a difference in how you lose weight and if you keep it off. 

There are a few reasons why men lose weight faster than women, including that men tend to have more muscle, and this burns calories more efficiently than fat. Although men may drop pounds more quickly, the average weight loss between men and women evens out over time.

And while it may seem that men lose belly fat faster than women, there is no real proof that this is true.

It’s possible that you burn calories more slowly than other people. How fast you burn them is based on your metabolism — chemical reactions that make energy from the food you eat.

If you have a slow metabolism, your genes may be to blame. 

Other things that can affect how you burn calories include:

Getting older. Your metabolism slows down about 2%-8% every decade. That may be from decreased muscle mass.

Eating too little. It sounds strange, but the truth is, if you skip meals or follow a very low-calorie diet, it can backfire by making you burn calories more slowly.

The more a person weighs, generally, the more calories they burn both when they’re active and when they’re at rest. This means if you cut enough calories, you could start losing weight quickly. As you start to lose weight, though, your body doesn’t need to burn quite as much as before, so your metabolism starts to slow down.

Self-protection. There’s another reason why it might be easier to lose weight at the start of your weight loss journey than after you’ve lost some pounds. It’s your body trying to protect you. When you take in fewer calories, your body starts to think that you’re in a famine and you won’t have food available. The body’s cells start storing fat to be used later. If there is extra weight, the body doesn’t need to store the fat at first, so you lose weight. But as the pounds start to go away, your body starts storing fat to protect you, making it harder for you to lose more.

Set point theory. There’s also something called set point theory. This is the belief that your body has a set weight that it will always return to. Salamon compares it to your home’s thermostat. Whether it’s cold or hot outside, your heating or cooling system will bring the temperature to the one you’ve set. The set point theory says that no matter how much weight you lose, it will eventually come back to a certain number.

Leptin. Leptin is the hormone that makes you feel full. People who are heavier have higher levels of leptin circulating in their body, so you would think that they would feel full faster than someone who is leaner. But heavier people also can develop leptin resistance, which means that they don’t feel after they’ve eaten. 

“Lack of sleep, whether it's quality or duration, can actually increase the amount of hunger hormone that we produce, ghrelin,” Salamon says. Ghrelin is the hormone that tells you it’s time to eat something. “Sometimes I have patients who may not have slept as well the previous night, and they find themselves more hungry than usual despite eating the same food as the day before. Inadequate quality of sleep or duration of sleep can increase our feelings of hunger, even if we're not truly experiencing it.”

When you're tired, you're more likely to make poor food choices you might not choose when you’re feeling more refreshed and alert, like choosing sweets over fruit. In a recent study, people who didn't get enough sleep ate about 300 more calories per day than those who got more rest. 

You may also have less energy when you don't get enough sleep, which makes it harder to exercise.

For some people, difficulty losing weight could be in their genes. Some bodies are better at burning fat than others. It's something you inherit from your parents or grandparents.

You don't have any control over the genes that were passed to you, so you may need to work a little harder to burn calories and lose weight.

If you have an underactive thyroid, you may have a condition called hypothyroidism. It can lead to weight gain from a buildup of salt and water in your body.

An overactive thyroid is called hyperthyroidism. Many people with it lose weight, but others pick up extra pounds because it can make you feel hungrier.

How your thyroid affects your metabolism, energy, and weight is complicated. Other hormones, proteins, and chemicals may also play a role. Check with your doctor if you think it's a problem.

Binge eating disorder, or BED, causes you to eat large amounts of food in a short period. This isn’t simply overdoing it at the dinner table or having an extra evening snack. It’s an uncontrollable urge, and you feel like you have no control over what you eat and how much of it. The definition for BED is bingeing at least once a week for three months.

If you’re concerned that you might be binge eating, speak with your doctor. There are psychologists who are binge eating specialists, and connecting with one might be what you need, Salamon says.

The environment plays a big role in how people eat. The environment doesn’t mean just where you are, but what is going on around you. This includes:

  • Having access to healthy foods, including having them available at work or school
  • Having the money to pay for those foods
  • Being physically active – and this includes having a safe place to do things like go for walks outside and having time to be active
  • Having family members who are also having difficulty with their weight, managing their food choices, and physical activity
  • Cultural expectations — the type of food that’s served as well as portion sizes

Some medical conditions can make it tougher to lose weight. A few issues that could be causing your weight problems are:

  • Heart disease
  • Hormonal disorders
  • Sleep disorders like sleep apnea

Some medicines can also deal a blow to your efforts to drop some pounds. For instance, you might have trouble losing weight if you take certain drugs for:

  • Allergies
  • Birth control
  • Depression
  • Diabetes
  • Epilepsy
  • High blood pressure
  • Bipolar disorder
  • Schizophrenia

If you have one of these conditions and weight is a problem for you, talk to your doctor. They can review your treatment plan to see if it can be affecting your weight.

Losing weight isn’t an easy thing to do, and it can be discouraging if you’re doing your best. But sometimes it’s the little things that make the biggest differences. While you can’t change everything (like having a medical condition), there may be things you can do, like ensuring you get enough sleep, lowering your stress levels, avoiding bedtime snacking, and eating breakfast. 

Why can't I lose weight on a calorie deficit diet?

Just lowering the number of calories you eat will not necessarily make you lose weight. A lot depends on the types of calories you’re eating, when you eat them, and if you’re physically active.

Why can't I lose weight after having a baby?

There are many reasons why someone might have trouble losing weight after having a baby. For some, the healthy diet they ate during pregnancy isn’t as easy to follow, while taking care of a new baby, so it might be easier and faster to grab whatever food is handy. Irregular sleep and meal times don’t help either, and getting physical activity can be challenging. There are still the hormones circulating in the body, which affects mood, appetite, and weight, too.

Why can't I lose weight on Ozempic?

Not all medications work for everyone, and the reason why you don’t lose weight if you’re taking Ozempic might not be the same as for someone else. You shouldn’t rely on Ozempic alone for weight loss. It needs to be incorporated with eating a healthy diet, getting enough physical exercise and sleep, and lowering stress levels if that’s a concern.

Is there a medical reason why I can't lose weight?

There could be a medical reason why you can’t lose weight. For example, people with hypothyroidism, an underactive thyroid, tend to gain weight.

How to lose weight fast?

There is no safe way to lose weight fast. The best way to lose it and keep it off is to do so slowly and with purpose.