If you’ve ever tried to lose weight and found the pounds won’t come off easily — or they come right back — you are not alone.

The fact is that when we shed pounds, we trigger mechanisms that make it hard to keep the weight off. Some factors are within our control, but many are not. Understanding how this works might make you look more kindly on your body.

I won’t tell you how to lose weight — or whether you even need to. But I will give you five realities to consider that may make it easier for you to understand.

1. Metabolism slows when you lose weight.

Your metabolism is the processes through which your body converts the food you eat into energy. Metabolism varies from person to person. Scientists don’t know everything about why that is. But they do know that part of that variation has to do with the composition of fat versus muscle in your body. It also varies by gender — men have faster metabolisms because they have more muscle on their bodies — and it slows as we age.

But for everyone, metabolic energy burn occurs in three main ways:

1. Resting metabolism — the energy used to keep your organs working and, basically, stay alive. This accounts for anywhere from 50% to 70% of the total calories you burn.
2. Thermic effect of food — the energy used to digest what you eat and turn it into energy, about 10% of the calories you burn.
3. Physical activity, which makes up about 30% of your calorie burn. Purposeful exercise (like hitting the gym) is usually a very small portion of this energy expenditure. Mostly, we’re talking about the energy used to move around.

When you lose weight, your metabolism slows, in part through simple physics.

2. If you choose to try to lose weight, make changes that you can live with for the long haul.

 In other words, make changes that you actually like, because you’ll need to stick with them to keep the weight off. That’s because losing weight triggers biological mechanisms that make it harder to keep the weight off — including a slower metabolism.

Metabolism seems to act like a spring: The more effort you put into losing weight, the more you can stretch that spring out — that is, lose weight. But if you let up the tension on the spring — by stopping whatever eating and exercise routine helped you lose weight — your metabolism will spring back and you’ll regain the weight you lost.

3. Hormones in your brain conspire to make you hungrier when you lose weight.

Here’s another diabolical change that happens when you lose weight: Your hormones change in ways that alter your appetite. While a lot of different hormones are involved in hunger, one of them is leptin, which is released by fat cells and basically tells your brain when to eat and when to stop eating. As you lose weight, your leptin levels drop, and when that happens it’s like a starvation signal. A lot of times, people seem to want to eat even more than they were eating before to kind of rapidly recover that weight loss.

4. To lose weight, what you eat is more important than how much you exercise.

 For most folks, exercise is a minor player in weight loss. The fact is that it’s a lot easier to cut out 600 calories by skipping a Starbucks muffin than it is to burn it by running for an hour or more.

What’s more, people tend to use exercise as an excuse to let themselves eat more. When that happens, they tend to eat more calories as a “reward” than they burned off at the gym. Or they might compensate by crashing out on the sofa and moving less the rest of their day.

But that shouldn’t be a reason not to exercise, just don’t do it so you can “earn” a piece of chocolate cake. There are many documented benefits to exercise that have nothing to do with weight loss, including better mood, better sleep, reduced anxiety and better blood sugar levels.

5. On the other hand, exercise seems to play a big role in maintaining a lower weight.

People who’ve lost weight and stuck to it for more than a year, report exercising every day for about an hour on average.

But that doesn’t have to mean gruelling workouts. The most popular form of exercise among adults who’ve lost weight is walking, but for a good 60 minutes per day.

One reason exercise seems to be a key to weight-loss maintenance is that it helps counteract some of those biological mechanisms that kick in when you lose weight — decreased metabolism and increased hunger. The difference between how much you want to eat and how many calories you are burning creates an energy gap.

So here’s something to bear in mind.  One reason it’s so difficult to lose weight and then to keep it off is that your brain and body are conspiring to alter and change, thus changing what your body needs along the journey.

You’ll need to be prepared to adjust your calorie intake up and down, to adjust your exercise levels up and down, to keep your brain engaged and to keep you on track.

Blog by Derrick Allott.