Insights from a general practice service evaluation supporting a lower carbohydrate diet in patients with type 2 diabetes mellitus and prediabetes: a secondary analysis of routine clinic data including HbA1c, weight and prescribing over 6 years

Summary

A UK GP practice offered a lower‑carb eating approach to patients with type 2 diabetes and prediabetes over 6 years and saw major improvements in blood sugar, weight, blood pressure, lipids, and a large drop in diabetes drug use and costs.

What the study did

From 2013–2019, a single GP surgery in England routinely offered patients with type 2 diabetes (T2D) or prediabetes straightforward guidance to reduce foods with higher glycaemic impact (sugars and starchy carbs) and choose lower‑GI options. Support was via brief one‑to‑one appointments plus optional group sessions. 199 people chose this approach and stuck with it long enough to have “baseline vs latest” measurements audited.

Key findings

• Type 2 diabetes (128 people; average 23 months on plan): - HbA1c (long‑term blood sugar) fell from a median of 65.5 to 48 mmol/mol (strongly significant). - Weight dropped from a median 99.7 kg to 91.4 kg. - Blood pressure fell by about 11/5 mmHg. - Lipids improved: triglycerides and LDL decreased; HDL increased; total/HDL ratio improved. - Drug‑free remission (HbA1c <48 mmol/mol without diabetes meds) was achieved by 46%. - People starting with the worst HbA1c improved the most. - The practice cut diabetes prescribing costs by £50,885 per year vs local average.

• Prediabetes (71 people; average 22 months): - HbA1c fell from a median 44 to 39 mmol/mol. - 93% reached a normal HbA1c (<42 mmol/mol). - Weight, blood pressure, and lipids improved in the same pattern.

Notes on the Study

• This is real‑world clinic audit data, not a randomized trial. There’s no control group, and participants self‑selected and persisted, so results may reflect motivation and support as well as diet.
• The dietary advice focused on lowering high‑GI/high glycaemic load foods (sugars and starches), using simple explanations and infographics; it did not require precise carb gram counting.
• Improvements were statistically significant across HbA1c, weight, BP, and lipid measures for those who chose and stuck with the lower‑carb approach.
• The study explicitly notes debate about long‑term adherence and safety of lower‑carb diets, but within this practice, outcomes and prescribing costs improved over years of routine care.
• The paper does not claim national generalizability; it calls for more empirical research.
• It does not prove causation; it reports associations within a practice‑based program.

Practical relevance for everyday people with diabetes or prediabetes

• Lowering foods that spike blood sugar (sugars and starchy carbs) — and choosing lower‑GI options — was associated with notable improvements in blood sugar, weight, blood pressure, and lipids in routine primary care.
• Many participants achieved drug‑free remission of type 2 diabetes; most with prediabetes returned to normal HbA1c.
• People with very high HbA1c saw the largest drops, suggesting potential benefit even when control is poor.
• The approach used brief appointments and group support, indicating it can be woven into everyday care without complex tracking.