You aren’t really following your diet 
Often times we start a diet with the best intentions. But intentions do not always equal actions. Sampling food as you cook, adding extra condiments or sauces, having a few cheat meals on the weekend all can completely derail your progress. Many individuals have not even realize they have gone off track. Take time to really look at all the aspects of what the diet entails and what you put in your mouth. Being honest with yourself is the best starting point. The true way to succeed with a diet is being consistent 80-90% of the time. 
 
You aren’t eating enough (especially protein) or your skipping meals
When you dip below about 1,200 calories per day, not only are you not eating enough to get all your nutrients, but your body slows your metabolism in order to hold on to precious calories for your vital organs. Also, if you skip meals to lose weight, your body could lose its ability to feel full. Blame evolution, which has designed our bodies to resist famine and not the buffet table. For example, if you skip breakfast, the body assumes food is scarce. You need a morning meal to let your body know it’s okay to burn calories. Make sure you eat within 1 hour of waking, getting protein and fiber to stoke the metabolic fire.

You’ve given into the no-carb or fat-free craze
Cutting back markedly on any one food group-say, carbs or fat, can leave you short on the nutrients you need to stay energized. Nutrient deficiencies puts you in higher odds of putting on belly fat. The trick is a varied diet that includes healthy fats and good carbs such as fruits. After all, the biggest reason low-carb diets backfire is that, for the vast majority of people, they aren’t sustainable over the long haul. And as with all diets, once you quit, you regain the weight you lost and (often) more. These fluctuations can make it an even bigger challenge to lose weight next time. In addition, I see many clients who go low carb and assume they can eat endless amounts of fats & protein. This is far from the truth as of these in excess will leave you packing on the pounds. 

You aren’t minding your portions
Food scale? Measuring cups? What are those?? All too common I see clients coming in and telling me they portion out their foods. However, when I inquire further I find out they are eyeballing out their servings. Research shows that we all have tendencies to under estimate portions of protein sources and overestimate servings of carbs and fats. The key to really seeing that scale shift is making your kitchen scale & measuring cups your best friends. An extra 5 minutes measuring can save you the headache of plateauing. 

You’re not keeping track of what you’re eating
Awareness is incredibly important if you are trying to lose weight. Many people actually don’t have a clue how much they’re really eating. Studies show that keeping track of your diet helps with weight loss. Many times our transformation challenge winners have been the ones most diligent with tracking their intake so they are accountable and actually know what they are putting in their mouths. Surprises may arise if you think you are 80% consistent and track, only to find out it is more like 50%. 

You’re stressed out
A hectic schedule, challenging job, social drama—whatever the reason for your stress, it may be the underlying cause of your weight loss struggles. That’s because of the stress hormone called cortisol, which may increase the amount of fat your body stores away.  In fact, research has shown that higher levels of cortisol have been linked to greater amounts of visceral fat. Even more reason to take a few deep breaths and look into ways to manage your stress levels.

You’re not getting enough sleep
Not only do we crave unhealthy comfort foods when we’re tired, but our sleep levels are linked to our hormone levels. People who are sleep-deprived tend to have more cortisol, so they’re more stressed out. Recent research has shown that sleep deprivation also impacts how our metabolism burns fat, turning to muscle as an easier energy source. 

You Have a Medical Condition That is Making Things Harder
There are some medical conditions that can drive weight gain and make it much harder to lose weight. These include hypothyroidism, polycystic ovarian syndrome (PCOS) and sleep apnea. Certain medications can also make weight loss harder, or even cause weight gain. If you think any of this applies to you, then speak to your doctor or seek a dietitian about your options.

You’ve been dieting for too long
Do you remember the last time you weren’t dieting or doing something to try to lose weight? If you’re not sure, you’ve probably been focusing on fat loss for too long. Most people who are unsuccessful in their weight loss tend to diet year-round. Typically, they go through periods where they’re “being good” and getting results, but then eventually fall off the wagon—hard.
Many people assume that if they’re not losing weight, it’s because they’re eating too much. So they eat less. This cycle of compliance/weight loss and non-compliance/weight gain becomes a pattern that can be hard to break. That’s because your body has a natural “set point,” a certain body weight or body-fat level it will fight to maintain.
Give your body a break! If you’ve been consistently dieting for more than three months, or if you’re spending way too much time fantasizing about the pastry shop down the street, take a break from dieting. Oddly enough, ending a diet can sometimes make it easier to lose weight. 

Your Expectations Are Unrealistic
Weight loss is generally a much slower process than most people want. Although it is often possible to lose weight fast in the beginning, very few people can continue to lose weight at a rate of more than 1-2 pounds per week. Another major problem is that many people have unrealistic expectations of what is achievable with a healthy diet and exercise. The biggest key to success is not focusing on the scale, but looking at the bigger picture of being consistent a majority of the time and becoming the strongest, fittest, healthiest version of yourself.