By Dan Remon · Evidence checked October 2026
A single can of sugar-sweetened soda contains up to 40 g of free sugars. WHO’s lower target for a whole day is roughly 25 g.
That doesn’t make sugar poison. The evidence is calmer than the headlines: clearest on weight and teeth, pointing the same way but mostly observational on diabetes and heart disease, and still unsettled on sweeteners. This page covers what it says, at what intake, and what I do with it.
For the practical side, how to stop the cravings, read 5 ways to stop sugar cravings.
Is sugar bad for you?
At high intakes, yes. Added sugar is generally more harmful than helpful, especially for heart and metabolic health, and the best-evidenced harms are weight gain and tooth decay. WHO recommends keeping free sugars under 10% of your daily energy intake and suggests going under 5% for extra benefit.1 A 2023 umbrella review in the BMJ found harmful associations between sugar and 45 health outcomes, though most of that evidence was observational and rated low quality.2 The sugar in whole fruit, vegetables and milk isn’t the concern. Sugar added to food and drink is, along with honey, syrups and fruit juice.
How much sugar is too much: the WHO limits
WHO’s 2015 guideline on sugars intake for adults and children makes 3 recommendations.1
- Reduce free sugars throughout life (strong recommendation).
- Keep free sugars below 10% of total energy intake, in adults and children (strong recommendation).
- Go further, to below 5% of total energy intake (conditional recommendation, which WHO words as a suggestion).
In grams: the guideline counts carbohydrate, sugars included, at 4 kcal per gram. On a 2,000 kcal day, 10% is 200 kcal, or 50 g of free sugars. 5% is 25 g, which WHO puts at roughly 6 teaspoons.3 Your own numbers move with how much you eat.
The 2 limits rest on different evidence. The 10% limit is based on moderate quality evidence from observational studies of tooth decay, alongside trials in adults where eating less sugar went with lower body weight. The 5% suggestion rests on very low quality evidence from national population studies of tooth decay, which is why it’s conditional. Blood fats, blood pressure and diabetes markers weren’t part of the review, and WHO listed them as questions for further research.1
What counts as free sugar
Free sugars are the sugars added to food and drink by the manufacturer, the cook or you, plus the sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates.1 The guideline doesn’t cover the sugars in fresh fruit and vegetables or the sugars naturally in milk, because there’s no reported evidence of harm from them.3
So a whole orange isn’t counted and orange juice is. Honey and syrup count, however natural the label makes them sound. Much of it sits in food you wouldn’t call sweet: WHO’s example is a tablespoon of ketchup, with around 4 g of free sugars.3 Read the labels on sauces, flavoured yoghurt, cereal and snack bars.
Sugar, weight, diabetes and heart health
Weight
The meta-analysis behind WHO’s guideline pooled randomised trials in adults eating freely. Cutting sugar lowered body weight by 0.80 kg on average and adding sugar raised it by 0.75 kg. When sugar was swapped for other carbohydrates at the same calories, weight didn’t change.4 So the effect appears to run through the extra energy. WHO puts it plainly: free sugars provide significant energy without specific nutrients.1 If weight is your main goal, effective weight loss for busy executives covers the full plan.
Type 2 diabetes
A 2015 meta-analysis of 17 cohorts found that each daily serving of a sugar-sweetened drink was associated with an 18% higher incidence of type 2 diabetes, and 13% after adjusting for body fat.5 That’s observational, so it can’t prove cause, but the link held after accounting for body fat. If you already have type 2 diabetes or prediabetes, your doctor’s advice comes first, and my post on type 2 diabetes covers what I focus on.
Heart health and the wider picture
The broadest view is a 2023 umbrella review in the BMJ, which pulled together 73 meta-analyses covering 83 health outcomes. It found significant harmful associations for 45 outcomes, including 18 endocrine and metabolic outcomes and 10 cardiovascular ones, and 4 beneficial associations. Most of the evidence was rated low or very low quality, and none was rated high.2
Among the firmest findings, rated moderate quality, the highest intakes of sugar-sweetened drinks were linked to higher body weight, and the highest intakes of added sugars to fat stored outside normal fat tissue, such as in the liver. At low quality, each extra 250 mL a day of sugar-sweetened drinks went with a 17% higher risk of coronary heart disease and a 4% higher risk of death from any cause. The authors recommend keeping free or added sugars below 25 g a day, about 6 teaspoons, and sugar-sweetened drinks to less than one serving a week, about 200 to 355 mL.2
My read: the case is strongest where WHO set its limits, on weight and teeth, and it points the same way for heart and metabolic health at lower certainty. Drinks are where the evidence and the easy wins line up.
Are sweeteners and diet drinks a better choice?
I’ve long argued that the problem is sweetness, not only sugar. Swapping a sugary drink for a diet one keeps the habit in place.
In 2023 WHO landed somewhere similar. Its guideline on non-sugar sweeteners suggests they not be used as a way to control weight or lower the risk of noncommunicable diseases. It’s a conditional recommendation based on low certainty evidence overall, and it doesn’t apply to people with pre-existing diabetes.6
The review behind it found 2 different pictures. In short-term trials, mostly 3 months or less, sweeteners led to slightly lower weight and BMI, but only when compared with sugar, and had no significant effect on glucose, insulin or blood fats. In long-term observational studies, higher intake was associated with higher BMI and a higher risk of type 2 diabetes, cardiovascular disease and death. WHO notes that reverse causation may explain part of that: people already concerned about their weight or health may be the ones choosing diet drinks. Its expert group also noted that sweeteners have no nutritional value.6
The 2015 diabetes meta-analysis found the same pattern: the link between diet drinks and type 2 diabetes fell from 25% to 8% per daily serving after adjusting for body fat, with signs of publication bias and confounding. Its authors still judged diet drinks and fruit juice unlikely to be healthy alternatives to sugary drinks for preventing type 2 diabetes.5
So my standard is water. If you want bubbles, soda water. Read the label on mixers like tonic water too. If plain water bores you, infused water is an easy upgrade. A diet drink can be a step on the way from sugary drinks to water. I wouldn’t make it the destination.
What I do with this: one lever at a time
Knowing the numbers doesn’t change what’s in your fridge. Start with a baseline. Blood work runs through Orba Health, the health company I co-founded, and its partners. Fasting glucose, HbA1c and triglycerides are a sensible starting set, and anything that needs medical attention goes to your doctor. Personalised nutrition covers what else is worth testing. You can’t upgrade what you refuse to audit.
Then change goes in through the Monthly Lever, the way every change goes in through the Stealth OS: one change, installed for one 28-day cycle, until it runs without thinking. The next cycle stacks on top of it. Try to fix sugar, sleep and training in the same week and the week wins.
For sugar, I start with drinks. They’re easy to count and easy to swap, and the umbrella review gave a clear target for them.
- Cycle 1: drinks. Sugary soft drinks, juice and sweetened coffee drinks out. Water, soda water, unsweetened tea and black coffee in.
- Cycle 2: hidden sugar. Read labels for a week, find where free sugars show up in sauces, cereal, yoghurt and snack bars, and swap the biggest sources.
- Cycle 3: the habits around it. The afternoon snack, dessert by default, the airport lounge. That’s where 5 ways to stop sugar cravings takes over.
Retest when the cycles are done, so you can see what changed in your own numbers.
How to start
Start with a baseline, then choose how much support you want.
- The 1% Scorecard. Free, 8 questions, 2 minutes. You get a score out of 100 and the one thing to install first.
- The Quest. The performance membership, if you want the system and the 28-day cycles without private coaching. Cancel anytime.
Start with what’s in your glass.
Related reading: The flow approach to nutrition: eat for performance without a diet, Nutrition coaching: what a coach does and what the evidence says and Adaptive metabolism: why the scale stalls when you diet.
FAQ
How much sugar per day is too much?
WHO recommends keeping free sugars below 10% of your daily energy intake and suggests going below 5% for extra benefit. On a 2,000 kcal day that’s 50 g and 25 g, and WHO puts 25 g at roughly 6 teaspoons. Sugars in whole fruit, vegetables and milk don’t count towards it.
Is the sugar in fruit bad for you?
WHO’s sugar guideline doesn’t cover the sugars in fresh fruit and vegetables, because there’s no reported evidence of harm from them. Fruit juice and juice concentrates do count as free sugars. Eat the fruit and skip the juice.
Is diet soda better than regular soda?
It has far less sugar, but WHO suggests not relying on non-sugar sweeteners to control weight or lower disease risk, based on low certainty evidence. Short trials showed small weight losses, while long-term observational studies linked higher intake to type 2 diabetes and cardiovascular disease, which may partly reflect who chooses diet drinks. Water or soda water is the better default.
Does sugar cause type 2 diabetes?
The studies linking sugar to type 2 diabetes are observational, so they can’t prove cause. In a 2015 meta-analysis of 17 cohorts, each daily serving of a sugar-sweetened drink was associated with an 18% higher incidence of type 2 diabetes, or 13% after adjusting for body fat. If you’re concerned about your blood sugar, get tested and talk to your doctor.
Sources
- World Health Organization. (2015). Guideline: sugars intake for adults and children. Geneva: World Health Organization. who.int/
publications/ i/ item/ 9789241549028 - Huang, Y., Chen, Z., Chen, B., Li, J., Yuan, X., Li, J., Wang, W., Dai, T., Chen, H., Wang, Y., Wang, R., Wang, P., Guo, J., Dong, Q., Liu, C., Wei, Q., Cao, D., & Liu, L. (2023). Dietary sugar consumption and health: umbrella review. BMJ, 381, e071609. doi.org/10.1136/bmj-2022-071609
- World Health Organization. (2015, 4 March). WHO calls on countries to reduce sugars intake among adults and children. News release. who.int/
news/ item/ 04-03-2015-who-calls-on-countries-to-reduce-sugars-intake-among-adults-and-children - Te Morenga, L., Mallard, S., & Mann, J. (2013). Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ, 346, e7492. doi.org/10.1136/bmj.e7492
- Imamura, F., O’Connor, L., Ye, Z., Mursu, J., Hayashino, Y., Bhupathiraju, S. N., & Forouhi, N. G. (2015). Consumption of sugar sweetened beverages, artificially sweetened beverages, and fruit juice and incidence of type 2 diabetes: systematic review, meta-analysis, and estimation of population attributable fraction. BMJ, 351, h3576. doi.org/10.1136/bmj.h3576
- World Health Organization. (2023). Use of non-sugar sweeteners: WHO guideline. Geneva: World Health Organization. who.int/
publications/ i/ item/ 9789240073616
This article is general information, not medical advice.
