French Researchers Find Simple Cooking Changes Stabilize Blood Sugar in Type 2 Diabetes

A study from France has uncovered a practical, food-based strategy that could help millions of Americans with type 2 diabetes gain better control over their blood sugar — without adding new medications. Researchers at the Centre de Recherche en Nutrition Humaine Rhône-Alpes, affiliated with INSERM and the Université Claude Bernard Lyon 1 in Lyon, found that simply switching to foods containing slowly digestible starch (SDS) — and learning how to prepare them properly — significantly reduced blood sugar swings over a 12-week period.

What the French Study Found

French nutrition scientists recruited 51 adults with type 2 diabetes who weren't meeting their blood sugar targets. Participants were randomly assigned to either a high-SDS diet or a low-SDS diet for three months. Both groups received specific starchy food products and personalized dietary and culinary coaching on how to prepare their meals.

Using continuous glucose monitors (CGMs) — the same technology increasingly popular among US diabetes patients — researchers tracked a key measure called Mean Amplitude of Glycemic Excursions (MAGE), which captures how dramatically blood sugar rises and falls throughout the day.

The results were striking: the high-SDS diet group saw their MAGE score drop by approximately 30.4 mg/dL more than the low-SDS group — a statistically significant improvement (P = 0.0025). Multiple other measures of blood sugar variability also improved, including day-to-day fluctuations and overall glucose consistency.

Perhaps most importantly for US patients: HbA1c levels in the high-SDS group fell below the 7% target — the gold standard recommended by the American Diabetes Association (ADA). Compliance throughout the study was an impressive 96%, suggesting this approach is realistic for real-world patients.

Understanding Slowly Digestible Starch

Not all carbohydrates are created equal. Slowly digestible starches break down gradually in the gut, releasing glucose into the bloodstream at a measured pace rather than all at once. Common sources include:

• Al dente-cooked pasta (slightly firm, not overcooked)
• Cooled and reheated rice or potatoes
• Legumes like lentils and chickpeas
• Less-processed whole grains
• Unripe or green bananas

Cooking methods matter enormously. Overcooking starchy foods speeds up digestion and raises blood sugar faster — something French culinary tradition, with its emphasis on technique, helped participants navigate effectively.

Why This Matters for US Patients

The United States has one of the highest rates of type 2 diabetes in the world, with over 38 million Americans currently diagnosed. Many struggle to reach the ADA's recommended HbA1c target of below 7% despite medication. This French research is valuable because it demonstrates that dietary adjustments alone — without changing medications — can push patients across that critical threshold.

France's research tradition in nutrition science, combined with its distinct food culture and culinary expertise, gives this study a unique perspective on how meal preparation techniques affect metabolic health. The structured cooking counseling used in this trial is something US dietitians and diabetes educators could readily adapt into existing programs like the ADA's Diabetes Self-Management Education (DSME).

Additionally, because the study used CGM technology — now widely covered by US insurance for type 2 diabetes patients — Americans can apply these same monitoring strategies at home to see how different foods and cooking methods affect their own blood sugar in real time.

The Bottom Line

Choosing and preparing starchy foods more thoughtfully may be one of the most accessible tools available for improving blood sugar control. Talk to your diabetes care team about incorporating slowly digestible starches and proper cooking techniques into your meal plan.

Source: Chisbert, Castell, Van Den Berghe. "Optimizing glycemic variability in type 2 diabetes using simple dietary and culinary recommendations to modulate starch digestibility: a randomized controlled trial." The American Journal of Clinical Nutrition, 2025. PMID: 41092985. DOI: 10.1016/j.ajcnut.2025.10.007