There's nothing more frustrating and disheartening when your hard work doesn't pay off, particularly when it comes to exercise and eating well.
Maybe you've been pushing your body to the limits training every day, or you've filled your diet with nothing but healthy, varied whole foods. But still the weight doesn't budge.
According to health experts, there are a few simple reasons why you're not losing weight -- and they don't all have to do with eating too much.
According to Chloe McLeod, an accredited practising dietitian and sports dietitian, much of the problem surrounding difficulty losing weight has to do with overly high expectations.
"Often people are wanting to lose three or four kilos in a week, or to lose it much too quickly for it to be safe or meet expectations. So it's about adjusting those," McLeod told The Huffington Post Australia.
"In relation to actually not being able to lose the weight, whether it's coming off way too slowly or not coming off at all, there are two main reasons why this will often be happening."
1. You aren't eating enough.
You're probably thinking, 'Eat more to lose weight? Surely that's not right'. It may seem counterintuitive, but if you're not eating enough, chances are you won't lose the weight.
"The most common reason people, particularly for women, aren't losing weight is they are not eating enough," McLeod said.
"Rather than eating too much, it also works the other way around. I see people all the time going on these ridiculous 1,200 calorie (or less) diets, plus they train for an hour to an hour and a half each day. And they say, 'I'm barely eating and exercise a lot, so I should be losing weight. But why aren't I?'
"This happens because there's not enough energy going in to fuel what they're doing, so their metabolism starts to slow down and, as a result, they struggle to lose weight."
It's like filling a car with half the petrol it needs to go a certain distance, but still expecting it to go the distance.
This idea is simple: eat more so you can do more.
"A good example of that is a client I recently saw. She has been training really hard and really cut back on her food to around 1,200 calories. She runs 30 kilometres a week and does boxing, but she couldn't lose those last couple of kilos. We looked at how much she was eating," McLeod said.
"I know it sounds counterintuitive to eat more to lose weight, but in that situation it was exactly what she needed to be doing."
Nutritionist Christine Cronau agrees.
"There are many popular programs and diets that advocate exercising hard and restricting calories, especially fat. However, this can set us up for failure," Cronau told HuffPost Australia.
"Our bodies need fuel to run effectively and when we exercise, we need more fuel, not less. Reducing fuel intake and doing hardcore exercise is very hard on the body. It's like filling a car with half the petrol it needs to go a certain distance, but still expecting it to go the distance."
"Your car is not going to run if it doesn't have enough fuel in it. So you need to be putting in enough fuel in order for everything to function well," McLeod added.
When we take in less calories than we need, (especially combined with exercise), our body goes into a state of "starvation stress", Cronau said.
"Our thyroid has to slow and our metabolism has to slow. What happens when we stop the punishing exercise routine and start eating again? We will generally gain the weight back, plus interest," Cronau explained.
2. You're eating too much (even if it's healthy food).
On the other side of the spectrum, if you are overconsuming food, weight loss will be harder. This one is obvious, but many people may not understand this still applies to healthy food.
"Maybe the person is actually eating too much, even if they're eating really healthy and exercising regularly. Even with these healthy choices, if there's too much going in, it can result in weight loss not occurring," McLeod said.
This comes down to the fact that weight loss = more energy out than energy in. That is, if your body is burning less energy (through exercising and your basal metabolic rate) than the energy you are eating (food), then this will not result in weight loss.
"A good example of that is maybe the person is exercising in the morning, then they have a really quick, small breakfast, go to work and don't have time for lunch. So they don't eat anything until later in the afternoon, but then they really overeat to overcompensate for missing out on the other meals," McLeod said.
"Even if they're making healthy food choices, it can still end up being too much overall."
Other times, our portion sizes for each meal and snack are simply too big.
"Yes, they're having a healthy breakfast, lunch and dinner, but over the course of the day it ends up being more than the body requires," McLeod said.
This isn't to say eat junk food because, well, what's the point -- not all calories are created equal and are metabolised differently in the body.
You can figure out how much energy you require in a day according to your age, height, weight and exercise level.
3. You're stressed.
When it comes to weight loss, stress is a two-pronged culprit: when you're stressed you likely eat more and, separately, your body may be less likely to lose weight.
"What I often see is people who are stressed are often stress eating. Even if they're making healthy food choices, it ends up being a bit more than usual which your body doesn't really need," McLeod said.
"Stress does have an impact on all your different hormones and how your body is able to utilise different things. It's definitely possible that stress can make it harder to lose weight.
"More commonly, though, the reason it's harder is because there's more food going in due to stress eating."
4. You're exercising too much.
According to Cronau, you can also put your body into stress (and inhibit weight loss) by exercising too much.
"We can actually end up doing more harm than good. If we have not fuelled our bodies correctly, exercise can be quite stressful, causing excess cortisol (the stress hormone) production, which often causes weight gain," Cronau explained.
5. You're eating too many 'healthy' foods.
Thanks to social media and online health 'experts', the message surrounding what's healthy and what's not can become skewed.
"People often think some foods are really healthy, such as raw treats or many raw snack bars, but they're often really calorie dense," McLeod said.
"Carbohydrate choice is also really important. If you're choosing white bread or processed foods, they don't fill you up enough. Even though they might have similar calories to the other less processed alternatives, because you get hungry quicker, you end up eating more overall."
6. You're not sleeping enough.
You guessed it: lack of sleep doesn't just have an effect on our mood and concentration.
"If you're not sleeping enough, that can actually have an impact on your ability to maintain a healthy weight," McLeod told HuffPost Australia.
"There's quite a lot of research around that now and the importance of getting enough sleep so your body is able to destress and function properly.
"On top of that, when you're tired, your body actually releases more of the hormones that make you feel hungry. This means, again, that you think you need food when your body doesn't really need it."
So, what are the solutions?
"Make sure that you're eating enough. Rather than counting calories and focusing on that, focus on fuelling yourself with plenty of fresh produce, whole grains, lean protein, and drinking plenty of water so that you're not accidentally eating when you're actually just dehydrated," McLeod said.
"Get plenty of sleep. And whether it's exercising as stress relief or meditating, practise different strategies to help with managing stress."