Sugary drinks

Sugar dissolved in a drink is absorbed almost instantly, so it drives a large, fast spike in blood glucose and insulin - bigger than the same sugar eaten in solid food. It also barely registers as "food": liquid calories don't fill you up, so you don't eat less to compensate. That combination of sharp metabolic spikes and low satiety is why sugary drinks strain your metabolism beyond their calorie count.

Imamura F et al. 2015

A meta-analysis pooling large cohort studies found that each additional daily serving of a sugar-sweetened drink was associated with about 18% higher risk of developing type 2 diabetes. Crucially, after adjusting for body weight the association only dropped to about 13% - it didn't disappear. So part of the harm runs through weight gain, but not all of it; the drinks appear to do something to metabolism on top of the calories.

Imamura F et al. 2015

The common defence - "it's just a small treat" - misses that the risk held even after accounting for weight. Because these are observational studies, some confounding is possible (people who drink more soda may differ in other ways), so read it as a strong, consistent association rather than proof. But "linked to higher diabetes risk beyond weight" is the honest summary.

Imamura F et al. 2015

Diabetes is not the only endpoint that has been pooled. A separate dose-response meta-analysis of prospective cohort studies reported that each additional daily serving of a sugar-sweetened drink was associated with about 9 per cent higher risk of cardiovascular disease, with a tight range around it. The same review looked at death from any cause and did not find a clear association - the range there included no difference at all, and it is reported here alongside the rest rather than left out. These reviews draw on overlapping sets of studies, so this is one evidence base describing two outcomes, not two independent confirmations of the same thing.

Meng Y et al. 2021

Not on the evidence this page rests on, and the honest answer is that it is a different and messier question. The review behind the heart figure here looked at artificially sweetened drinks as well and reported associations for them too, but that literature is harder to read: people often switch to diet drinks because they are already worried about their weight or their blood sugar, which pushes the association in a direction that has nothing to do with the drink. Nothing on this page recommends a diet drink as the fix, and nothing here says one is harmful. The fix is water because water is the option no evidence argues against.

No. Both figures come from pooled observational studies, so people drinking more sugary drinks differ from those drinking fewer in diet, income, activity and much else, and adjustment never removes all of it. What makes the diabetes association more interesting than most is that it did not disappear when researchers accounted for body weight - it fell from about eighteen per cent to about thirteen. That suggests the link is not only about the calories, which is a claim about where the association sits, not a demonstration that the drinks produced the disease.