I went from 90kg to 72kg. That is 18kg, not 20, and it took the guts of a year around a full-time job and two kids. I am 37. I mention it because most 20kg plans are written by people who have never had to do it during a working week with a school run attached, and the difference is not the science. The science is simple. The difference is what happens in month five.
How long does it actually take?
Half a kilo a week is the sustainable rate. Twenty kilos at that pace is forty weeks of losing, and nobody loses for forty consecutive weeks. Real life inserts a holiday, a Christmas, a fortnight where everything falls apart, and a few stretches where you deliberately stop and hold.
So: nine months to a year. If that sounds slow, compare it to the last four attempts that were meant to take eight weeks. This is the one that finishes.
Going faster is possible and mostly counterproductive. A brutal deficit strips muscle alongside the fat, which is what leaves people lighter but somehow softer, and it is unholdable for the length of time 20kg actually needs.
What each stage feels like
This is the part nobody publishes, and it is the part that decides whether you finish.
The first 5kg. Fast, encouraging, and partly water. Clothes change quickly, everyone tells you it is working, and you assume this is the rate. It is not the rate. Enjoy it, but do not set your expectations here.
5 to 10kg. The real work starts. The scale slows to something that looks like nothing on a weekly view, people stop commenting, and the novelty has worn off. This is where the majority of attempts die, and they die from boredom rather than hunger.
10 to 15kg. Things get genuinely easier. Moving is easier, you are visibly different in photographs, and the habits have stopped being decisions. The main risk here is complacency: the deficit has quietly shrunk because you are lighter, and the same eating no longer produces the same loss.
15 to 20kg. Slowest stretch of the lot, and the point where the last of it comes off the places it always leaves last. See how to lose belly fat for why that is genetics rather than effort.
The number you actually need
Not 1,200 calories. Your own maintenance, minus a few hundred. Work it out with the TDEE calculator, take 300 to 500 off, and get your protein target from the macro calculator. Both are free, no email, no signup.
Then recalculate every 5kg. This is the single most common reason a plan that worked for three months suddenly does not: a lighter body burns less energy doing exactly the same things, so the gap closes without you changing a thing. Nothing broke. The arithmetic moved.
Protein is what decides whether the 20kg you lose is fat or a mix of fat and muscle. Aim for 1.6 to 2.2g per kg of bodyweight, and see how much protein per day for what that looks like in real Irish shopping. Sleep does the same job from the other direction.
Getting leaner is not the same as looking better
The thing nobody tells you: there is a point where continuing to lose makes you look worse, not better.
I hit it. I had been eating around 2,100 calories for a long stretch and the number on the scale kept obliging, and I looked flat. Tired. The kind of lean where people ask if you are alright rather than what you have been doing. What fixed it was eating more, not less. I went back up to maintenance, kept training, and looked considerably better at a heavier bodyweight than I had at the lighter one.
That is not a paradox, it is what muscle does. Two people at the same weight can look completely different depending on what that weight is made of, and past a certain point the thing standing between you and looking how you want is not another kilo off. It is more muscle under the skin, which requires eating.
So set the target as a look, not a number. If you have 20kg to lose, the number is a fine guide for the first fifteen. Somewhere in the last five it stops being the right scoreboard, and continuing to chase it is how people end up small and unhappy instead of lean.
Maintenance is a productive phase, not failure
Deliberately stopping is a tool, not a relapse. Most people only ever stop by accident, feel like they have failed, and either quit or crash harder. Planning the stop changes what it does.
A few weeks eating at maintenance in the middle of a long run does several useful things. It gives you a break from the mental load of a deficit, which is what actually runs out before willpower does. It lets you practise the thing you will have to do forever, because maintaining is a skill and nobody arrives at their goal weight having ever done it. And it is much easier to restart a deficit you paused on purpose than one that collapsed on you in week nineteen.
For a 20kg target, expect to spend real time at maintenance. A year of losing, straight through, is not what this looks like for anyone with a job and a family. Losing, holding, losing again is not a slower route. It is the route that gets there.
What about 10kg?
Same method, roughly half the time: four to six months. Everything above applies, with one advantage worth naming, which is that 10kg is close enough to picture from day one. Twenty is abstract at the start, and the way through that is to run it as four separate 5kg jobs rather than one enormous one.
What actually makes it work
- A deficit you can hold. 300 to 500 under maintenance. The aggressive version is not faster over a year, because you will not be doing it in month four.
- Protein at every meal. It protects muscle and keeps you full, which is the same problem solved twice.
- Steps. Walking widens the deficit without making you ravenous the way a punishing session can.
- Lifting two to four times a week. This is what makes the end result look how you pictured it.
- Recalculating every 5kg. The stall is arithmetic, not metabolism.
- Planned maintenance breaks. Not a failure. Part of the plan.
Starting from nothing? Fat loss basics covers the first three properly. If you are already doing all of this and nothing is moving, read why weight loss stalls.
Frequently asked questions
Do I need to give up takeaways? No. You need to fit them in. A plan that bans the Friday takeaway for a year is a plan that ends in March.
Should I weigh myself daily? Daily is fine as long as you compare weekly averages rather than yesterday. A single morning can swing two kilos on salt and sleep alone and tells you nothing.
Will I have loose skin? Possibly, depending on age, how long the weight was on and how much there is. Losing slower and keeping muscle helps. Nobody can promise you otherwise, and anyone selling a cream for it is selling a cream.
Is 20kg safe to lose? At half a kilo a week, for most people, yes. If you have a medical condition, are on medication that affects weight, or are significantly heavier than 20kg above a healthy range, talk to your GP first so it is being done with someone watching.
This is general education, not medical advice. If you have a health condition or are on medication, talk to your GP before starting a deficit.