Swiss Study Says Young Type 1 Patients May Not Need to Count Carbs with Smart Pumps

A study from Switzerland is challenging one of the most burdensome daily tasks for young people living with Type 1 diabetes: counting every carbohydrate gram at every meal. Researchers at the University Children's Hospital in Zurich found that teenagers and young adults using a hybrid closed-loop insulin delivery system maintained equally good blood sugar control whether they counted carbohydrates precisely or simply selected a general meal size category — no math required.

What the Researchers Did

The trial, called SMASH (Simplified Meal Announcement Study using Hybrid closed-loop), enrolled 46 young people aged 12–20 with Type 1 diabetes across two Swiss university hospitals. Participants used the mylife CamAPS FX closed-loop system — combining the YpsoPump insulin pump with a Dexcom G6 continuous glucose monitor (CGM) — for two separate 3-month periods. During one period, they counted carbohydrates traditionally. During the other, they used a simplified approach, choosing from individualized meal size categories (such as small, medium, or large) without calculating exact grams. The order was randomized.

What They Found

The results were striking in their similarity. Participants spent 69.9% of time in their target glucose range using the simplified meal announcement method, compared to 70.7% using traditional carb counting — a difference of just 0.6 percentage points, well within the study's non-inferiority margin of 5 points.

In US-friendly numbers, the target glucose range used was 70–180 mg/dL (converted from 3.9–10.0 mmol/L), which aligns directly with the American Diabetes Association (ADA) recommended Time in Range (TIR) target of over 70% for most people with Type 1 diabetes.

Time spent below 70 mg/dL (hypoglycemia) was nearly identical: 1.8% with simplified announcement vs. 1.9% with carb counting. Time above 180 mg/dL was also comparable: 28.2% vs. 27.2%. Total daily insulin was slightly higher with the simplified method (54.0 vs. 51.7 units/day), but blood sugar outcomes remained equivalent. No intervention-related serious adverse events occurred.

Why This Matters for US Patients

Carbohydrate counting has been a cornerstone of Type 1 diabetes management for decades, and US guidelines from the ADA still recommend it as a key mealtime insulin dosing strategy. However, this Swiss research suggests that for young people using advanced hybrid closed-loop technology — systems increasingly available in the US, including the Tandem Control-IQ and Omnipod 5 — precise carb counting may no longer be essential to achieving good glucose control.

This is especially meaningful for American families. Carb counting creates significant daily stress for children, teens, and parents — particularly in school settings, at restaurants, and during social events. Simplifying meal announcements could reduce diabetes burnout, improve quality of life, and potentially improve long-term adherence to therapy without sacrificing safety or effectiveness.

While the CamAPS FX system used in this study is not currently FDA-approved in the United States, the underlying closed-loop algorithm principles apply broadly. US patients and providers should discuss whether simplified meal announcement approaches might be appropriate with currently available AID (Automated Insulin Delivery) systems.

The Bottom Line

This rigorous Swiss clinical trial provides compelling evidence that the next generation of smart insulin pumps may free young Type 1 patients from one of diabetes management's most tedious burdens — without compromising their health outcomes.

Source: Laesser, Piazza, Schorno. "Simplified meal announcement study (SMASH) using hybrid closed-loop insulin delivery in youth and young adults with type 1 diabetes: a randomised controlled two-centre crossover trial." Diabetologia (2025). DOI: 10.1007/s00125-024-06319-w. PMID: 39560745.