Blood glucose responses to carbohydrates may reveal subtypes of metabolic health

Differences in how individuals respond to carbohydrates could help identify distinct subtypes of metabolic health, according to new research from Stanford Medicine, Palo Alto, California. The findings could pave the way for more personalised approaches to preventing and treating prediabetes and Type 2 diabetes.

The study, led by Professor Michael Snyder and Professor Tracey McLaughlin, found that blood sugar responses to specific carbohydrate-rich foods varied depending on underlying metabolic conditions such as insulin resistance or β-cell dysfunction. Both conditions contribute to high blood sugar levels and increase the risk of developing diabetes.

“Current dietary guidelines from the American Diabetes Association are not always effective because they treat everyone the same,” said Dr. Snyder, who is the Stanford W. Ascherman professor in genetics.

“This study shows that not only are there subtypes within prediabetes, but your subtype may determine which foods you should or should not eat,” he said.

First authors include Dr Yue Wu, a postdoctoral scholar in genetics; Ben Ehlert, a graduate student in biomedical data science; and Dr Ahmed Metwally, formerly of Stanford and now a research scientist at Google. The findings were published on 4 June in Nature Medicine.

The study involved 55 participants without a previous diagnosis of Type 2 diabetes. Of those, 26 had prediabetes – a proportion that reflects national statistics, with one in three adults in the United States estimated to have the condition.

Participants underwent metabolic testing for insulin resistance and β-cell function, alongside comprehensive multi-omics profiling. This included blood triglyceride levels, liver function tests and gut microbiome data.

Each participant wore a continuous glucose monitor and consumed the same-sized portions of seven carbohydrate-rich foods:

• jasmine rice
• buttermilk bread
• shredded potato
• pasta
• canned black beans
• grapes
• a berry mix.

The foods were consumed at 10 to 12-hour fasting, with each food eaten twice.

The researchers observed that many participants experienced glucose spikes after consuming rice or grapes, irrespective of their metabolic health. However, responses to foods containing resistant starch – notably potatoes and pasta – were more variable and appeared to correlate with insulin resistance or β-cell dysfunction.

“Starchy foods were not equal; there was a lot of individual variability in which foods produced the highest glucose spike,” said Dr. Wu.

Those with insulin resistance recorded the highest spikes after eating pasta, while both insulin resistance and β-cell dysfunction were associated with spikes after eating potatoes. These participants also exhibited elevated levels of triglycerides and fatty acids, markers commonly associated with insulin resistance.

Beans prompted glucose spikes linked to histidine and keto metabolism – a state in which the body primarily uses fat for energy. Meanwhile, those who spiked after eating bread were more likely to have hypertension.

Notably, participants with both insulin resistance and poor β-cell function exhibited the strongest glucose responses to potatoes. Almost all participants showed some level of spike after eating grapes. Comparing the blood sugar responses to grapes and potatoes appeared to be a potential biomarker for insulin resistance.

“Such a biomarker would be useful because insulin resistance can be treated through lifestyle changes and medication,” said Professor McLaughlin.

“At present, there is no easy way to diagnose it in the clinic,” she said.

The researchers also tested whether eating a portion of fibre, protein or fat before consuming carbohydrates could modulate blood sugar spikes. Participants consumed pea fibre powder, egg white protein or crème fraîche 10 minutes before eating rice.

Among metabolically healthy individuals, consuming fibre or protein reduced the glucose spike, while fat delayed the peak. However, these benefits were not observed in participants with insulin resistance or β-cell dysfunction.

Even so, the team believes that the timing of food intake warrants further exploration.

“Eating carbohydrates later in a meal is still a good idea, even though it remains unclear whether it is best to precede them with protein, fat or fibre,” said Professor Snyder.

“Eat your salad or hamburger before your chips,” he concluded.

For further reading please visit: 10.1038/s41591-025-03719-2