The truth is, everyone wants to lose weight fast. But the thing is, the weight didn’t come on overnight, and it’s not going to leave that way, either. So, then, how fast is realistic? As a general guideline, most experts say weekly losses of 0.5 to 2 pounds are doable. “A pound a week is really good for most people,” says Dr. Angela Fitch, a diplomate of the American Board of Obesity Medicine and associate professor of internal medicine at the University of Cincinnati. “But many people think it should be easier than it is. They lose 5 pounds in a month and think that’s not enough. No, that’s an amazing job!” And, what’s more, it’s healthy. After all, when you lose weight too fast, you risk losing weight not just from fat, but also from lean tissue such as muscle. That’s part of the reason why, when bariatric patients undergo programs designed for faster weight loss (like, 12 to 18 pounds lost per month), they do so under the supervision of a physician and medical staff who ensure patients receive the necessary nutrients to prevent muscle-wasting and other serious health issues, says Dr. Craig Primack, a member of the national board of directors for the Obesity Medicine Association. So if you’re trying to lose weight on your own, and about a pound per week is your goal, what determines if you get there? Here, experts explain nine surprising factors that influence how fast (or slow) you lose weight:

YOUR CURRENT WEIGHT

Contrary to popular lore, your current body mass (aka weight) is the No. 1 determinant of your metabolic rate, or how many calories you burn per day; the larger you are, the higher your metabolism, Primack explains. To lose weight, you need to consume fewer calories per day than you burn. So, someone who weighs 300 pounds and burns 2,800 calories per day can cut more daily calories to lose weight faster than someone who weighs 150 pounds and burns 1,800 calories per day, he says. (Note: most experts recommend not cutting daily calories below 1,200.)

YOUR WEIGHT-LOSS HISTORY

Have you lost weight in the past? Unfortunately, you’re already at a disadvantage, explains Dr. Michael W. Schwartz, chair of the task force that authored the Endocrine Society’s scientific statement on obesity's causes. That’s because when you lose weight your metabolic rate drops lower than it should, based on pure body size. For example, if two women both weigh 180 pounds, but one of them used to weigh 250, all else being equal, she will burn 25 to 30 percent fewer calories per day, he says. That makes her efforts to continue losing weight far more difficult.

YOUR LIFESTYLE

“The more bandwidth people have to make those changes, the faster they lose weight,” Fitch says. “How many changes you make determines how much outcome you can get from them.” Translation: If you’re already living a pretty healthy lifestyle, the needle is likely going to move more slowly. However, if you’re starting from zero, you have a lot of room from improvement in your nutrition habits, activity levels and likely other lifestyle factors such as sleep and stress that impact your weight-loss success, she says.

HOW FAR YOU ARE INTO YOUR WEIGHT-LOSS JOURNEY.

“Most people lose weight more quickly at beginning of a diet,” explains Denver-based registered dietitian Jessica Crandall, a spokesperson for the Academy of Nutrition and Dietetics. While the degree of changes that people are able to make in the first days and weeks of a weight-loss plan certainly has something to do with it, plenty of other factors play a role. For instance, as mentioned earlier, while you lose weight your metabolism slows, making future weight loss more sluggish, Fitch says. That often leads to a drop in resolve that can water down people’s efforts – and slow weight loss even more, Crandall says. Lastly, it’s important to remember that in the early days of weight loss, most drastic drops in the scale aren’t due to fat losses, but rather drops in water weight. This is most true in people who reduce their carbohydrate intake, Crandall says. That’s because when your body stores carbs in your liver and muscles it stores water molecules along with them. So, when you reduce your carb intake and, therefore, your body’s reserves of stored carbs (called glycogen), your body’s water levels decrease, and it shows up on the scale, she says.

YOUR HORMONAL HEALTH

Hormones are chemical messengers, instructing cells within your body as to what they should and shouldn’t do – and that includes losing weight. “Some people have abnormal functions of thyroid and cortisol hormones that promote weight gain and weight retention,” Fitch says. “We usually check patients for these in the office.” In women specifically, the hormonal factors that can affect weight-loss rates are plentiful. For example, with polycystic ovary syndrome, which, according to one Clinical Epidemiology review, may impact up to 20 percent of all women of childbearing age, insulin resistance is a common result, making weight gain likely and weight loss exceedingly difficult. Hormonal changes around perimenopause and menopause are another fly in the ointment: “If a woman goes through menopause without making changes, she will gain midsection weight,” Fitch says. If you believe hormonal issues may be having any negative effect on your weight-loss efforts or overall health, talk to your doctor.

YOUR WORKOUT OF CHOICE

“Aerobic exercise burns calories and makes our heart healthier, but you also need to build some muscle, or just work to maintain the muscle you do have when you lose weight,” Fitch says. That’s because when you lose weight some of that weight naturally comes from muscle – and when muscle levels decline, so does your metabolism, slowing your future weight-loss results. To build lean, metabolically active muscle, integrate strength training at least twice weekly into your workout routine. Note: When building muscle, you may actually notice your weight loss slowing. After all, a given volume of muscle weighs more than the same volume of fat, she says.

YOUR GENETICS

“The biggest thing that makes a difference in how different people lose weight is genetics,” Primack says. “It is estimated that 20 major genes and 200 or more minor genes impact fat storage and weight maintenance.” However, knowledge is power. And while direct-to-consumer genetic testing companies allow you to test your genes (including some weight-related ones) at home, simply talking to the people on your family tree can give you a lot of insights into what you may have inherited, he says.

YOUR SLEEP HABITS

“The amount of sleep you get makes a large difference in your metabolic rate and how fast you are able to lose weight,” Primack says. “People who sleep less than seven hours per night tend to have slower metabolisms.” Meanwhile, no matter how many hours you log per night, if that sleep is poor quality, it can also affect your metabolism and increase your body’s cravings – which can slow your weight-loss progress, Crandall says. Sleep apnea, for example, is consistently linked with weight problems. And while sleep apnea and weight are a bit of a chicken-and-egg scenario, treating sleep apnea can help speed up people’s weight-loss, she says.