Important considerations for low carbohydrate eating and diabetes management

What is a low carbohydrate diet?

Low-carbohydrate (low-carb) diets are increasingly used in clinical practice to support glycaemic management, weight reduction, and cardiometabolic health, particularly for people living with type 2 diabetes. However, the term “low-carb” is often used broadly and inconsistently. In practice, low-carbohydrate eating exists along a continuum of carbohydrate intake, rather than as a single, uniform dietary pattern.

Understanding the different levels of carbohydrate restriction, their potential benefits, and key considerations is essential when supporting clients who choose or are advised to follow a lower-carb approach.

Different levels of carbohydrate intake

Low-carbohydrate diets can be classified by total daily carbohydrate intake:

Moderate-low carbohydrate

~100–130 g carbohydrate per day

• Often considered the upper threshold for low-carb eating
• Aligns with reductions from typical Australian intakes without extreme restriction
• Emphasises:
  • Reduced refined grains and added sugars
  • Smaller portions of wholegrains and starchy vegetables
  • Increased non-starchy vegetables, protein, and healthy fats

For many clients with type 2 diabetes, this level offers a practical, sustainable approach and may be suitable for long-term use. For people with type 1 diabetes, moderate carbohydrate reduction may reduce post-prandial glucose excursions while maintaining dietary flexibility.

Low carbohydrate diet

~50–100 g carbohydrate per day

• Greater reduction in breads, cereals, rice, pasta, and some fruit
• Swapping to lower carb bread products, noodles, rice and pasta
• Non-starchy vegetables become the primary carbohydrate source
• Protein intake typically increases to support satiety and muscle mass
• Often used to improve glycaemic control and weight loss

This approach is commonly used in type 2 diabetes to achieve greater improvements in HbA1c, glycaemic variability, and weight outcomes. In type 1 diabetes, this degree of restriction requires careful insulin adjustment and close glucose monitoring and may not be appropriate for all individuals.

Very low-carbohydrate / ketogenic diet

<50 g carbohydrate per day (often 20–30 g)

• Carbohydrate intake is sufficiently low to induce nutritional ketosis
• Most grains, fruits, legumes, and some vegetables are excluded
• Fat becomes the primary energy source

While such diets have demonstrated short-term glycaemic and medication-reducing benefits in type 2 diabetes under supervised conditions, they are not recommended as standard care for people with type 1 diabetes, due to increased risks of hypoglycaemia and diabetic ketoacidosis. [i][ii] [iii]

Potential benefits of low-carbohydrate diets

Evidence supports low-carbohydrate dietary patterns as an option for people with type 2 diabetes, particularly in the short to medium term.

• Reduction in HbA1c levels
• Reduction in body weight
• Improved satiety and appetite regulation – higher protein and fat intake can support hunger control
• A greater reduction in the risk factors for heart disease (triglycerides, HDL cholesterol and blood pressure)
• Reduced medication requirements (in some individuals, with appropriate supervision)
• Diabetes remission (very low carb diet)

It is important to note that individual responses vary, and benefits are influenced by diet quality, adherence, and baseline metabolic health.

There are very few studies investigating the long-term safety and effectiveness of low carb eating for people with type 1 diabetes. A 2018 review revealed some studies showed improvements in HbA1c while others showed no effect.  This review concluded that more, high-quality studies were needed to determine the overall impact of low carb diets on blood glucose management in individuals with type 1 diabetes. [iv] [v]

Considerations for type 1 diabetes

Key risks

Current guidelines do not recommend ketogenic or very low-carbohydrate diets as routine care for type 1 diabetes, particularly in children and adolescents. However, if clients are looking to make some modifications to their carbohydrate intake, consider the following risks:

• Hypoglycaemia risk
  Reduced carbohydrate intake without appropriate insulin adjustment increases risk, particularly during the transition phase.
• Diabetes ketoacidosis (DKA)
  Very low-carbohydrate diets can increase the risk of DKA, especially in insulin pump users or during illness.
• Nutritional adequacy and rigidity
  Highly restrictive dietary patterns may compromise fibre intake and increase the risk of disordered eating behaviours. [vi]

Quality counts

Low-carbohydrate does not automatically equate to healthy.

A well-constructed low-carb diet should emphasise:

• Non-starchy vegetables (fibre, micronutrients)
• High-quality protein sources (fish, eggs, lean meat, poultry, dairy, tofu, legumes where tolerated)
• Healthy, unsaturated fats (olive oil, nuts, seeds, avocado)
• Adequate fibre intake through vegetables, certain fruit, seeds, and permitted plant foods

Poorly planned low-carb diets may be low in fibre, overly restrictive, or high in saturated fat and highly processed foods.

Clinical considerations

Medication adjustments

• Reduced carbohydrate intake can significantly lower blood glucose levels
• Insulin and medication doses may need adjustment to reduce hypoglycaemia risk
• Close monitoring is essential, particularly during the early phase

Nutrient adequacy

• Fibre intake may fall if vegetables are insufficient
• Calcium, iodine, and certain micronutrients may require attention if food groups are excluded

Individual suitability

Low carbohydrate diets may not be appropriate for:

• Pregnancy or breastfeeding (without specialist input)
• Individuals with eating disorders
• Some renal conditions
• Patients unable or unwilling to sustain dietary restriction
• People at risk of malnutrition (such as elderly people with type 2 diabetes).
• People who take SGLT2 inhibitors as this may increase the risk of diabetes ketoacidosis.

Sustainability and preference

• Long-term success depends on alignment with personal preferences, cultural food patterns, and lifestyle
• A moderate- low-carb approach may be more sustainable for many individuals

Practical tips

• Frame low-carb eating as one option, not the only approach
• Start at ~130 g/day and adjust based on response and goals
• Emphasise food quality, not just carbohydrate grams
• Encourage self-monitoring of blood glucose to guide individualisation
• Collaborate with a diabetes health professional where possible e.g. accredited practising dietitian, credentialled diabetes educator, or an endocrinologist

References

[i] Goldenberg JZ, et al. Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis. BMJ. 2021;372:m4743.
[ii] American Diabetes Association. Standards of Care in Diabetes—2023. Diabetes Care. 2023;46(Suppl 1).
[iii] Peters AL, et al. Euglycemic diabetic ketoacidosis. Diabetes Care. 2015;38(9):1687–1693.
[iv] Leow ZZX, et al. Low-carbohydrate diets in type 1 diabetes: a systematic review. Diabetes Obes Metab. 2018;20(7):1705–1714.
[v] Turton JL, Raab R, Rooney RB. Low-carbohydrate diets for type 1 diabetes mellitus: A systematic review. PLoS ONE 2018; 13(3):e0194987
[vi] Smart CE, et al. ISPAD Clinical Practice Consensus Guidelines 2018: Nutritional management. Pediatr Diabetes. 2018;19(Suppl 27):136–154.

By Rebecca McPhee, Accredited Practising Dietitian