3. Your Muscle Mass Is Increasing
While you may be getting fitter and building lean muscle on the inside, the numbers on the scale may not reflect that. That’s because fat takes up more space than muscle, so when you become leaner and pack on denser muscle while losing fat, it’s likely that you may not weigh less, and may even weigh more, according to the Cleveland Clinic. You may have heard the phrase “muscle weighs more than fat,” which isn’t technically true as a pound of fat weighs the same as a pound of muscle. What is true is that the volume of fat and muscle are very different.[3]
When you put on 10 pounds of fat, it’ll take up more space and you’ll look softer, but when you put on 10 pounds of muscle, you’ll look leaner. “Per unit volume, muscle weighs more than fat, so shedding fat and gaining muscle may not immediately change the scale but will result in changes in shape, tone, and measurements,” says McGowan.[3]
In other words, you may look leaner as you build muscle and lose fat, but you may actually start to weigh more. While this won’t happen right away — it may take about a month or two, according to the Cleveland Clinic — this may be one reason why you see the numbers on the scale creep up even as you become more fit.

What You Can Do
Don’t stress about the numbers on the scale, or even your body mass index (BMI), which estimates the amount of body fat by using your height and weight. While BMI is better at estimating body fat than a simple scale, it does not distinguish between fat mass and body mass, and it doesn't accurately measure the full amount of fat in the body, according to research.[4]
Observe how your body is changing, rather than obsessing over the numbers on the scale, and check in with your doctor to make sure you’re hitting the right goals for you. Remember that losing fat and gaining muscle both play an important role in improving your health.

4. You’re Not Fueling Your Workouts Sufficiently
When embarking on a weight loss journey, you may think that eating less and exercising more is a silver bullet, but it’s not that simple. If you’re routinely skipping breakfast and working out on an empty stomach, for example, you may be more likely to overeat, says Melissa Majumdar, RD, the metabolic and bariatric coordinator at Emory University Hospital in Atlanta. “With timing your meal or snack and exercise, you have to be aware of overall calorie intake because your hunger may increase with additional exercise,” she says.

What You Can Do
Time your snacks and meals according to when you exercise. Majumdar recommends watching not only what foods you eat and portion sizes but when you eat in relation to when you’re working out. She advises making sure that you’re not skipping meals but that you are eating enough before exercise.

Eating healthy snacks before and after workouts can help prevent overeating. A review found that eating a light meal before and after exercise (compared with fasting before exercise or not eating after exercise) resulted in the least amount of calorie intake after finishing workouts.[5]
Your body needs a combination of protein and carbs to fuel and help build and repair muscles. Aim to eat at least one to four hours before a workout and about an hour after exercise.[6]
Good options for preworkout snacks include an apple with peanut or almond butter, or oatmeal with low-fat milk and fruit. Good postworkout options include low-fat yogurt with fruit.[6]
5. You’re Overdoing It on High-Protein Supplements or Carbs
For some people, the opposite of not eating enough before exercise can apply — they try to fuel their workouts too much. It can be all too easy to fall into the trap of thinking you need to chow down on protein shakes or bars, or load up on carbs, to boost your workouts.

Protein, says McGowan, is important for feeling full and satisfied after eating, and it is the building block for muscle. “Protein bars, protein shakes, and other high-protein supplements can be a great addition to a person’s nutrition plan, particularly when training hard or when trying to preserve muscle mass while losing weight,” he says. “But too much of a good thing can be problematic, and overemphasizing protein may lead to excess calories without additional benefits.”

What You Can Do
When choosing protein supplements, McGowan advises reading nutrition labels carefully and avoiding products that contain high amounts of sugar and fat.

And while carbohydrates are a vital energy source, you should also avoid adding extra to your plate, says McGowan. “Protein, carbohydrates, and fats should be consumed in a balanced ratio to provide energy, amino acids, and the healthy fats necessary for the body’s function,” he explains. “Just as disproportionate protein can lead to caloric excess, overemphasizing carbohydrates can lead to weight gain and may interfere with weight loss.”

Bottom line: If you want to build muscle with exercises such as resistance training, "it is generally considered best practice to use a food-first approach to add protein to your diet," says Lance Walker, a physical therapist at Oklahoma State University in Stillwater and an expert in sports who advises often on weight loss. As for eating extra carbohydrates, says Walker, it's not necessary even for competitive athletes, unless they're engaging in endurance sports such as marathons or triathlons.

More Strategies to Manage Weight Gain After Starting a New Workout Plan
Now that you know what may be behind this surprising and confounding phenomenon, here are some more tips that may help you move past it as you work to achieve your weight loss goals.

Remember: It’s temporary. While it’s understandable that you may feel disheartened by not getting the scale readings you were expecting to see, keep following the healthy eating and fitness plan you’ve crafted with your doctor or other healthcare provider. Many of the factors that may be contributing to weight gain before weight loss are temporary or will diminish over time.

Track your average weight over time. “When we talk about weight management and trying to lose weight, we want to look at an average,” says Dr. Tewksbury. She notes that someone may gain 3 pounds in the first week and then lose 2, and that it’s normal for weight loss to be very gradual and fluctuate.

Instead of weighing yourself daily, consider doing it once per week. Better yet, avoid the scale during the early stages of starting an exercise program, says Majumdar, and rely on other barometers of progress such as how clothes are fitting, especially if your new workout plan has you building muscle.

Keep a food journal. Writing down or using an app to record what you’re eating is an important part of a weight loss program. According to a review, there is solid evidence that people who keep track of what they are eating lose more weight while using a weight loss program and regain less of it back after the program ends. The review also found that easy-to-use electronic tools, such as apps, when used alongside a weight management plan, can make it even easier to keep a food journal and improve weight loss compared with paper and pen self-monitoring tools.[7]
People will often consume extra calories without realizing it because they’re exercising on any given day or treat themselves because they did exercise. “We actually underestimate how many calories we’re eating, and we overestimate how many calories we’re actually burning with exercise,” says Tewksbury. “We typically don’t recommend that people add additional food to compensate for calories burned while exercising.”

Work with a registered dietitian. If you’re looking to try and lose weight and change your diet and exercise routines, seek advice from a registered dietitian-nutritionist, says Tewksbury. She notes that a dietitian can help you figure out what to do, how to do it, and how to keep up with it over time.

Plus, they can help you identify what factors may be interfering with weight loss or even tipping the scales higher than before you started dieting and exercising. “If you start making behavioral changes and you’re not seeing what you were working toward after a certain amount of time, there might be something else going on,” says Tewksbury.

The Takeaway
If your goal is to lose weight and you’re not yet seeing results, rest assured it’s likely temporary. Yet being aware of the factors that may be getting in the way of your aim is key, as is knowing how to overcome them. To increase your chances for reaching your target weight in a healthy and sustainable way, talk to your doctor to make sure you don’t have any conditions that may affect weight loss — such as hypothyroidism or diabetes — and consider working with a healthcare professional such as a registered dietitian.

Take heart, stay the course, and keep working on your health and fitness plan to move toward your weight management goals, and know that it will all be worthwhile in the long run.