Open Food Labels. Search 352 ingredients⌘K

Review · Critical reviews in clinical laboratory sciences · 2016Conflicts declared

Sugar, metabolic disease and obesity: the state of the controversy

Stanhope KL · Free full text

What it found

The evidence linking added sugar to heart disease, type 2 diabetes and fatty liver is mixed.

Some studies in people find harm, others find none, and the authors say the missing definitive studies keep the controversy alive.

What they found

Studies in people

Population studies

Many studies link higher added sugar intake to fatty liver, unhealthy blood fats, insulin resistance, heart disease and type 2 diabetes. These links often remain after accounting for body weight and total calories.

Diet trials in people

Several trials found that people eating more sugar had higher blood fats, more liver fat and lower insulin sensitivity than those eating less. Some of these trials were limited because people ate their own diets, so the total sugar eaten was unknown.

Studies finding no harm

Some trials and meta-analyses found no harmful effects of sugar on risk factors like uric acid or blood fats. The authors note these were often funded by industry or had design problems.

Brain response to sugar

Brain imaging studies show that fructose and glucose affect the brain differently, and that sugar can activate reward areas. This may help explain why people might overeat sugary foods.

Weight gain from sugar

Some trials found that people eating more sugar gained more weight than those eating less, but these studies had limitations. One controlled trial found more weight gain on a high-sugar diet, but fiber differences and lack of blinding may have affected the results.

Animal and lab studies

Direct effects of fructose

The fructose part of sugar is taken up by the liver without regulation, which can lead to fat build-up in the liver, changes in blood fats, lower insulin sensitivity and higher uric acid. These effects may happen even without weight gain.

What the authors conclude

  • They say that definitive studies are still missing, which keeps the controversy alive.
  • They call for clinical trials lasting at least 4 weeks in healthy people, using energy-balanced diets with different sugar levels, and with objective measures of compliance.
  • They argue that filling these evidence gaps may be necessary to support policy changes that help make the food environment less likely to promote obesity and metabolic disease.

How it was done

The authors wanted to explain why the debate about sugar and health continues, and why settling it matters for public health policy.

They reviewed the evidence on whether added sugar directly or indirectly promotes metabolic disease, including studies in people, animals and cells. They also examined why some studies disagree and what research is still needed.

What it can’t tell you

  • Many of the studies in people were not designed to prove cause and effect, so they can only show links.
  • The animal and cell studies cannot show what happens in people.
  • The review cannot say what would happen if everyone ate a certain amount of sugar, because the needed long-term trials have not been done.

The paper

Title
Sugar consumption, metabolic disease and obesity: The state of the controversy
Type
ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
Evidence
Studies in people · animals · lab
Summarised from
Full text
Cite
Stanhope KL (2016). Sugar consumption, metabolic disease and obesity: The state of the controversy. Critical reviews in clinical laboratory sciences. doi:10.3109/10408363.2015.1084990Free full textPubMed 26376619DOI

Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error