The article reviews dietary strategies like low-carb diets, intermittent fasting, and plant-based diets for managing type 2 diabetes. It also highlights the need for personalised approaches to improve outcomes.

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Introduction

Type 2 Diabetes Mellitus (T2DM) is a global public health concern, characterised by chronic hyperglycemia due to insulin resistance and impaired insulin secretion.

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Emerging dietary strategies

1. Low-carbohydrate (LCHF) and ketogenic diets

Mechanism: Low-carbohydrate diets (typically <130g/day) and ketogenic diets (<50g/day) reduce glucose availability, prompting the body to utilise fatty acids and ketones as primary energy sources. This reduction in carbohydrate intake directly impacts postprandial glucose and insulin levels.

Evidence: Studies demonstrate that low-carbohydrate and ketogenic diets can significantly improve HbA1c, reduce body weight, and lower the need for antidiabetic medications. A systematic review and meta-analysis indicate a reduction in HbA1c by 0.5-1.0% over 6-12 months on low-carbohydrate diets.

Considerations: While effective, these diets require careful monitoring of renal function, lipid profiles, and potential for hypoglycemia, especially when patients are on insulin or sulfonylureas.

2. Intermittent fasting (IF)

Mechanism: Intermittent fasting involves cycling between periods of eating and fasting, which can enhance insulin sensitivity, promote weight loss, and reduce inflammation. Popular IF patterns include 16:8 (16 hours fasting, 8 hours eating) and the 5:2 diet (5 days normal eating, 2 days restricted intake).

Evidence: Clinical trials have shown that intermittent fasting can lead to reductions in fasting glucose, and insulin levels, and improved HbA1c, particularly in overweight and obese individuals with T2DM.

Considerations: IF must be individualised, especially in patients prone to hypoglycemia or those with eating disorders. It is contraindicated in patients requiring strict medication timing, such as with certain insulin regimens.

3. Plant-based diets

Mechanism: Plant-based diets emphasise whole grains, legumes, vegetables, fruits, nuts, and seeds, and exclude or limit animal products. These diets are rich in fibre, antioxidants, and anti-inflammatory compounds, which aid in glycemic control and cardiovascular health.

Evidence: A randomised controlled trial reported a 0.4% reduction in HbA1c over 22 weeks in participants following a plant-based diet, with improvements in weight, cholesterol, and insulin sensitivity.

Considerations: Adequate intake of vitamin B12, iron, and protein should be ensured, as deficiencies can occur if the diet is not well-planned.

4. Mediterranean diet

Mechanism: The Mediterranean diet, characterised by high consumption of olive oil, nuts, vegetables, fruits, and whole grains, and moderate fish and poultry intake, has been linked to reduced insulin resistance and improved glycemic control through its high content of monounsaturated fats and polyphenols.

Evidence: A meta-analysis of 19 studies found that adherence to a Mediterranean diet was associated with a 19% reduction in the risk of developing T2DM and significant reductions in HbA1c and fasting glucose levels in those with existing diabetes.

Considerations: Portion control of high-calorie foods like nuts and olive oil is necessary to avoid weight gain, which could counteract glycemic benefits.

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Case study 1

Patient profile: A 52-year-old male diagnosed with type 2 diabetes for 8 years.

His current medications are:

• Metformin 1000 mg BID
• Glimepiride 2 mg QD

Recent HbA1c: 8.2%

BMI: 29 kg/m²

Challenges: Difficulty in adhering to traditional calorie-restricted diets, episodes of hypoglycemia, high fasting blood glucose levels.

Intervention

The patient was counselled on adopting a low-carbohydrate diet, targeting a daily intake of 100-120 grams of carbohydrates, primarily from non-starchy vegetables, nuts, seeds, and moderate amounts of berries. Emphasis was placed on the inclusion of lean proteins and healthy fats (e.g., olive oil, and avocados). He was educated on carbohydrate counting and meal timing to optimise glycemic control without causing hypoglycemia.

Outcomes

 After 3 months, the patient reported significant improvements in his energy levels, fewer episodes of hypoglycemia, and better satiety between meals. His HbA1c decreased to 6.9%, and his fasting blood glucose levels stabilised within the target range (90-110 mg/dL). His BMI reduced to 27 kg/m², reflecting a 4 kg weight loss, primarily from abdominal fat.

Discussion

1. This case illustrates the effectiveness of a low-carbohydrate diet in improving glycemic control and weight management in T2DM.
2. The individualised approach, focusing on patient education and gradual dietary modifications, contributed to adherence and positive outcomes.
3. It highlights the importance of continuous monitoring and adjustment of dietary strategies to align with the patient’s clinical status and preferences.

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Case study 2

Patient profile: A 45-year-old patient was diagnosed with Type 2 Diabetes for 5 years.

His current medications are:

• Metformin 500 mg BID
• Vildagliptin 50 mg QD

Recent HbA1c: 8.0%

BMI: 30 kg/m²

Challenges: Struggling with weight management, high postprandial blood glucose levels, and inconsistent meal timings due to a busy work schedule as a schoolteacher.

Background

The patient had been experiencing difficulties with adhering to a traditional calorie-restricted diet due to her erratic work schedule. She reported frequent snacking on carbohydrate-rich foods, particularly during late evenings, contributing to poor glycemic control and weight gain. After discussing various dietary strategies, she expressed interest in intermittent fasting (IF) as a manageable approach that could fit her lifestyle.

Intervention

A patient was advised to adopt a 16:8 intermittent fasting regimen, where she would fast for 16 hours and have an 8-hour eating window, from 11:00 AM to 7:00 PM. This timing was chosen to align with her daily routine and allow her to have lunch and dinner within the eating window.

Key aspects of the intervention 

1. Meal composition: Focus on balanced meals with low glycemic index (GI) foods, including whole grains (millets, brown rice), lean proteins (chicken, fish, legumes), healthy fats (nuts, seeds, olive oil), and plenty of vegetables.
2. Hydration: Encouraged to drink water, herbal teas, and black coffee during the fasting period to maintain hydration and manage hunger.
3. Avoiding refined carbs: Minimised refined carbohydrates such as white bread, sweets, and sugary beverages, especially during her eating window.
4. Monitoring and adjustment: Regular follow-up every two weeks to monitor glucose levels, assess dietary adherence, and adjust medication if necessary.

Outcomes

After 3 months of following the intermittent fasting regimen:

Glycemic control: Mrs. S.K.’s HbA1c reduced from 8.0% to 6.7%. She reported more stable blood glucose levels throughout the day, significantly improving her postprandial readings.

Weight loss: She lost 5 kg, reducing her BMI to 28.4 kg/m², with noticeable reductions in abdominal fat.

Improved energy and focus: A patient reported increased energy levels and better focus during her work hours, attributing this to her structured eating pattern and avoiding late-night snacking.

Medication adjustment: Due to improved glycemic control, her Vildagliptin dose was reduced to 50 mg every alternate day.

Discussion: This case demonstrates the feasibility and effectiveness of intermittent fasting in managing Type 2 Diabetes among Indian patients, particularly those with busy lifestyles. The structured eating window helped the patient manage her meal timing, reduce calorie intake, and improve overall dietary quality. The intervention not only improved her glycemic control but also contributed to weight loss and enhanced overall well-being. The key to success was individualised support, careful monitoring, and alignment of dietary strategies with the patient’s routine and preferences.

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Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

The author of this article: Ms Rutambhara Nhawkar is a Clinical Dietician, M. Sc. (Clinical Nutrition & Dietetics),  certified diabetes educator and a medical writer from Pune.