There’s a reason your diet should change regularly when you’re losing weight. No diet will work for you forever, no matter how good it works when you first start.

That’s often a tough realization for people to come to. They are so happy that they’ve got it figured out, the pounds are dropping off, and for the first time ever, they’re feeling confident about their body.

It’s all moving in the right direction for weeks, maybe even a few months.

Then, suddenly, and seemingly without warning, you hit a brick wall. You completely plateau and no matter how strict you are, the scales just won’t budge.

You look down between your feet every morning and see the same number, day after day. After having had a friend or partner step on the scales, just to confirm that they’re not jammed on that number; you’re left wondering – what happened? What went wrong?

Truth is, you didn’t necessarily do anything wrong. You just might be unaware of why a diet works, and thus, why it must evolve over time.

Why diets work

You lose weight because you consume fewer calories than you expend. That is basic science. While people have tried to say it is more complicated than that, they’re looking at the wrong thing.

Some think you must avoid carbs to lose weight (or fat, or meat, or gluten, or eating after 6 pm, or breakfast, or sugar, or a million other things).

Any or all those things might work, but they work because you consume fewer calories than you expend.

Why you consume fewer calories than you expend might vary.

Perhaps certain diets suppress your appetite.  Some shorten your eating window, so you have less time to fit meals in, while others are avoiding foods that typically make you crave more and overeat.

The mechanism for how they work varies, but why they work is always the same. You consumed less than you expended.

Working out your baseline expenditure

Before knowing how much to consume, it follows you need to work out roughly how much you expend daily.

There are various calculations and ways of doing this, but they are all essentially taking you to the same place. They give you a baseline number of calories which you are expending each day.

This is based on your basal metabolic rate (BMR) – that is the number of calories your body would burn at rest, to sustain itself. Keep blood pumping, organs functioning and everything else your body is doing without your conscious effort, to keep you alive.

On top of the BMR, we add a rough number of calories based on your activity level, to come up with your total daily energy expenditure (TDEE).

A Google search will bring up calculators you can plug your numbers into if you want to do this for yourself.

Working out your weight loss number

Now that you know your TDEE you can work out how many calories to consume to lose weight. This is usually between 5 and 20% under your TDEE, depending on how aggressive you want to be, how much weight you must lose, etc.

If you followed a diet randomly, without knowing these numbers, that is fine. Just be aware that it is working because your consumption is less than your TDEE.

Now, this is where people start to trip up.

Why did a diet work for a while, and then stop working?

If you look at the calculation for your BMR and TDEE they are based on body weight. These numbers are never perfectly accurate because every person is different and so many factors are having an impact simultaneously.

Other things alter your actual expenditure such as muscle mass, hormonal balance, immune system, age, stress, etc. etc.

However, think about it – when you lose weight, it will change the numbers in the calculation.

Say you’re 200lbs and you are eating at 10% under your TDEE.

Over a couple of months, you manage to lose 20lbs, and suddenly progress slows to a halt. Why?

Of course, you’ve lost 10% of your bodyweight. Now you’re 180lbs, but you still have an equation based off being 200lbs.

You should consistently recalculate and change your diet as you progress if you want it to keep working.

As you lose weight, you need even fewer calories.

Start with the minimum effective dose

You should start your diet with the minimum effective dose. That means you want to aim for losing weight while making it as easy as possible.

Have as little hunger, disruption to your routine, additional thinking, discomfort, and deprivation as possible, while still being able to make progress.

This sets you up perfectly for being able to do a little bit more each time you meet a mini plateau.

If you start too aggressively, you have nowhere to go when things start to slow down. You’re already challenging yourself, and pushing too hard makes it unsustainable.

You start being hungry all the time, tired, lacking energy, craving foods and wanting to binge; if you’re trying to over diet.

Instead, you want to make it as easy and gentle as you possibly can. Realistically, dieting shouldn’t be especially painful until you are already very lean and trying to get ripped. For a general weight loss diet, you do not need to be aggressive.

Be realistic on timeframes

That being said, you need to be realistic about the speed you are losing weight. A non-aggressive diet will not lead to aggressive weight loss.

Most people trip up because they aren’t consistent for long enough.

Don’t get frustrated by slow progress, just recognize you are in it for the long haul and making progress week after week in a steady way is going to get you to your goal sooner. The tortoise will always beat the hare because the tortoise has staying power.