Swapping sugary drinks for zero versions does move the scale. The move is just smaller than you would hope.
In a large 2025 trial, the gap after one year was about 2 kg.
A one-year trial found a 2 kg gap
Europe's SWEET study took 341 adults with overweight or obesity, put them on a two-month low-calorie diet until they had lost more than 5% of their weight, then gave one group sweetener products and the other sugar products for ten months.
The sweetener group held onto more of the loss, and their gut bacteria showed no bad shifts.
Here are the numbers. Trading sugar for sweeteners is one way to build a deficit, not a drug that removes fat on its own.
| Comparison | Weight change |
|---|---|
| Sweetener group (1 year) | Less regain |
| Sugar group (1 year) | More regain |
| Gap between the groups | About 2 kg |
One can of soda is a fifth of your daily deficit
A 250 ml can of cola is 105 kcal. The zero version is 0–5 kcal.
If you are aiming for a 500 kcal daily deficit, swapping one can covers a fifth of it. Two cans cover two fifths.
| Drink, 250 ml | Calories | Sugars |
|---|---|---|
| Cola | 105 kcal | 26 g |
| Zero cola | 0–5 kcal | 0 g |
| Orange juice | 110 kcal | 22 g |
| Water or sparkling water | 0 kcal | 0 g |
The WHO says not to use them for weight control
In 2023 the World Health Organization advised against using non-sugar sweeteners for weight control.
The evidence that they lower weight long term is weak, and the effects of taking them for years are still not well understood.
That recommendation is conditional, and the WHO labeled its own certainty as low.
Trials pointing the other way have appeared since, like SWEET in 2025. The fair reading right now is: better than sugar, worse than water.
What you replace is sugary drinks, not water
- •If you drink sugary drinks, switching to zero pays off
- •If you drink water, there is no reason to switch to zero
- •If zero drinks lead you to extra dessert, the swap cancels out
If quitting all at once is too hard, keep one glass a day. Holding out and then drinking a lot at once is worse.
If the scale has not moved since you switched
Change the drink and leave everything else, and the daily deficit is around 100 kcal. That comes to about 400 g a month.
The needle is moving. It is moving less than the scale swings from one day to the next.
Skipping a third of a bowl of rice instead of the drink gives you the same 100 kcal. Which one is easier to live with depends on you.
Sources · SWEET randomized trial (Nature Metabolism, 2025) · WHO guideline on non-sugar sweeteners (2023) · Korea's Ministry of Food and Drug Safety food nutrient database