Low-Carb High-Fat Diets May Increase Type 2 Diabetes Risk by 20%, Long-Term Study Finds

Low-carbohydrate, high-fat diets, popular for weight loss, could actually increase the risk of developing type 2 diabetes by 20%.

A large 17‑year Australian study of nearly 40,000 Melbourne residents reveals that popular low‑carbohydrate, high‑fat diets—often adopted for quick weight loss—may actually increase your risk of developing type 2 diabetes by about 20%.

Study Overview

Participants & Timeline: 41,513 adults aged 40–69 enrolled between 1990–1994 as part of the Melbourne Collaborative Cohort Study; 39,185 were followed up until 2007 .
Dietary Assessment: Researchers calculated a “Low‑Carbohydrate Diet (LCD) score” based on the percentage of calories from carbohydrates, fats, and proteins. Higher scores indicate fewer carbs and more fats/protein in the diet .
Findings: Those eating ~38% of energy from carbs had a 20% higher risk of type 2 diabetes compared with those eating ~55%; adjusted incidence rate ratio (IRR)=1.20 (95% CI: 1.05–1.37) .

How Obesity Fits In

Mediation analysis showed that body mass index (BMI) explained about 76% of the link between low-carb diets and diabetes. After adjusting for BMI and waist-to-hip ratio, the association disappeared—making obesity the central driving factor .

Why Low‑Carb Diets Can Backfire

Experts explain the mechanism:

Lower carbs → more fats consumed, often saturated fats → weight gain & insulin resistance .
Reduction in fiber-rich foods like whole grains and legumes → worsened metabolic health .

Balance Is Key: Prioritizing Quality Carbs, Healthy Fats & Protein

Co-author Prof. Barbora de Courten (Monash & RMIT) emphasizes:

“We know that diets high in processed, fiber-poor carbohydrates and refined sugars can lead to weight gain. … This study shows that a low‑carb intake may increase long-term risk of type 2 diabetes through obesity, possibly due to higher fat consumption and low-fiber foods.”

The researchers advocate for a balanced diet rich in:

Minimally processed, fiber-rich carbohydrates (e.g., whole grains, legumes)
Monounsaturated and polyunsaturated fats (e.g., olive oil, nuts, fatty fish)
Adequate lean protein (e.g., seafood, poultry, legumes)

This model resembles a Mediterranean-style diet, long associated with reduced diabetes risk.

What This Means for You

Short‑term low‑carb diets can aid short-term weight loss or diabetes reversal—particularly when well-structured and doctor-supervised, as seen in recent trials using apps like Defeat Diabetes [New clinical evidence].
Long‑term low‑carb patterns that emphasize high-fat, low-fiber processed foods may lead to weight gain and ↑ diabetes risk.

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