Frequently Asked Questions

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Low-carbohydrate diets for metabolic health: A clinical FAQ

Introduction

Insulin resistance happens when your body’s cells stop responding well to insulin. This causes blood sugar to rise and forces your body to make even more insulin to compensate. It’s a major driver of Type 2 Diabetes, metabolic syndrome, and heart disease.

Low-carbohydrate diets can help prevent and manage these conditions by reducing how hard your insulin system has to work. When you eat fewer carbs, your body needs less insulin, which can improve how well your cells respond to it over time.

This FAQ offers practical, evidence-based guidance on using low-carb diets safely to improve metabolic health and reduce insulin resistance in clinical settings.

A low-carb diet reduces foods that raise your blood sugar—mainly sugars and starches like bread, pasta, rice, potatoes, sweets, and sugary drinks. Instead, you eat more protein, healthy fats, and non-starchy vegetables.

How much carbohydrate?

  • Low-carb: Less than 130 grams of carbs per day (under 26% of total calories)
  • Very low-carb (ketogenic): Less than 50 grams per day, which puts your body into a metabolic state called nutritional ketosis

What you eat:

  • Meat, poultry, fish, eggs, cheese
  • Nuts, seeds, olive oil, butter, cream
  • Plenty of leafy greens and non-starchy vegetables

What you limit:

Processed foods and added sugars

Low-carb diets improve health through several mechanisms:

1. Better blood sugar control
 Eating fewer carbs means smaller spikes in blood sugar and insulin after meals.

2. Reduced hunger
 Protein and fat keep you feeling full longer, making it easier to eat less and stick to the diet. This supports weight loss.

3. Improved fat burning
 Lower insulin levels help your body tap into stored fat for energy, reducing overall body fat—especially visceral fat (the harmful fat around your organs).

4. Stable energy and fewer cravings
 Cutting out refined carbs and sugars keeps your blood sugar steady throughout the day, preventing energy crashes and reducing food cravings.5.

5. Beneficial ketones
 When carb intake is very low, your body produces ketones. These molecules fuel your cells and also act as signals that reduce inflammation, decrease oxidative stress, and positively influence gene expression.

Low-carb diets can help many adults with metabolic health issues, especially those with:

  • Type 2 diabetes or prediabetes – improves blood sugar control
  • Overweight or obesity – supports weight loss and reduces hunger
  • Metabolic syndrome or insulin resistance
  • High triglycerides
  • Fatty liver
  • High blood pressure

Proven benefits include:

  • Lower blood sugar levels (HbA1c)
  • Reduced insulin production
  • Lower triglycerides 
  • Higher HDL (“good”) cholesterol
  • Lower blood pressure

Other potential benefits

Early research suggests low-carb diets may also help with:

  • Mental health conditions like bipolar disorder and schizophrenia
  • Fertility problems 
  • PCOS
  • Digestive disorders such as irritable bowel syndrome, reflux and also inflammatory bowel disease  (Crohn’s disease or ulcerative colitis).
  • Neurodegenerative diseases (like Alzheimer’s or Parkinson’s)
  • Skin conditions
  • Type 1 diabetes management
  • Kidney disease

Who needs extra caution?

Some people should work closely with their healthcare provider, including those:

  • Taking insulin, sulfonylureas, or SGLT2 inhibitors (risk of dangerously low blood sugar)
  • With kidney disease
  • Who are pregnant ( contraindicated in breastfeeding due to risk of ketoacidosis) 
  • Those with serious mental illness, especially those taking lithium or sodium valproate. 

Always consult your doctor before starting a low-carb diet if you have existing health conditions or take medications.

A nutritionally complete low-carb diet includes:

Non-starchy vegetables
 Eat plenty of leafy greens, broccoli, cauliflower, peppers, zucchini, and other low-carb vegetables. These provide essential vitamins, minerals, and fibre.

Adequate protein
 Include meat, poultry, fish, eggs, cheese, or plant-based proteins at each meal to maintain muscle mass and keep you satisfied.

Healthy fats
 Use olive oil, avocados, nuts, seeds, butter, coconut oil and fatty fish. These provide energy and help absorb nutrients.

Whole, minimally processed foods
 Choose foods as close to their natural state as possible—fresh vegetables, whole cuts of meat, real cheese, and whole eggs rather than packaged or processed alternatives.

Limit refined carbs and sugars
 Avoid or minimise bread, pasta, sweets, sugary drinks, and processed snacks.

Key principles:

  • Quality matters: Focus on nutrient-dense, high-quality foods
  • Sustainable: Choose a pattern you can stick with long-term.

Low-carb diet

Provides 50–130 grams of carbs per day (roughly 10–40% of calories). It improves blood sugar control, supports weight management, and enhances metabolic health by reducing your body’s reliance on glucose as the main energy source.

Ketogenic (keto) diet

 A very low-carb approach that provides fewer than 20–50 grams of carbs per day. This shifts your body’s primary fuel source from glucose to fatty acids and ketones (produced from fat), creating a metabolic state called nutritional ketosis.

Yes. Many randomised trials and reviews show that low-carb diets can produce meaningful improvements in:

  • Weight
  • HbA1c (blood sugar control)
  • Fasting glucose and insulin
  • Triglycerides
  • Blood pressure
  • Liver function tests for those with fatty liver disease.

These benefits are especially strong when carbohydrate intake is reduced and total calorie intake naturally decreases.

Important notes:

  • Evidence quality varies between studies.
  • Results depend on how the diet is implemented (food quality, calories, adherence).
  • Long-term effects need more research.

Clinical approach: Use low-carb as one evidence-based option among other dietary approaches, monitoring outcomes and adapting based on each patient’s response.

Short-to-medium term (months to a few years):
Safe for most people when well-planned and monitored.

Long-term (many years):
Limited data available. Main concerns include:

  • LDL cholesterol rises in some people
  • Nutrient deficiencies if the diet is poorly planned

Safety depends on:

  • Careful patient selection
  • Proper medication management
  • Diet quality (focus on whole, minimally processed foods.

Clinician action: Regularly monitor lipids, kidney function, electrolytes, and nutritional status as appropriate.

Before starting:

  • Review diagnosis and current medications (especially insulin, sulfonylureas, SGLT2 inhibitors)
  • Check kidney function
  • Confirm not pregnant/breastfeeding
  • Screen for eating disorder history

Medication plan:

  • Reduce insulin and sulfonylureas to prevent low blood sugar
  • Discuss SGLT2 inhibitor risks
  • Plan for possible blood pressure medication adjustments

Starting the diet:

  • Set a realistic carb target
  • Advise drinking plenty of fluids
  • Ensure adequate electrolytes (especially salt)
  • Provide food lists and meal examples

Follow-up:

  • Schedule early contact (within 2 weeks)
  • Review symptoms, blood sugar readings, and medication changes

Urgent warning signs (assess immediately):

  • Low blood glucose, if on insulin or a sulfonylurea, may indicate dehydration, severe low blood sugar, or low blood pressure.
  • Dizziness or fainting, especially if on blood pressure medications

Insulin and sulfonylureas

The greatest risk of hypoglycaemia is if carbohydrate intake drops without dose adjustment. Proactive dose reductions are often required.

SGLT2 inhibitors

These drugs can increase the (rare) risk of euglycaemic diabetic ketoacidosis, especially when:

  • carbohydrate intake is very low
  • the patient is acutely ill
  • the patient is dehydrated.

Clinician action

  • Write a medication adjustment plan before starting
  • Check that fasting insulin is greater than 10 or that C-peptide is not low, as low insulin levels increase the risk of ketoacidosis.
  • Provide written sick-day rules
  • Ensure ketone monitoring if the patient takes SGLT2 inhibitors or insulin 

Baseline measurements:

  • HbA1c
  • HOMA-IR (fasting glucose and insulin)
  • Fasting lipids
  • Apo B
  • Kidney function and uric acid
  • CRP
  • Liver function tests
  • Weight/waist circumference/blood pressure/
  • Current medications

Early follow-up (2–12 weeks):

  • Blood sugar review (if on diabetes medications)
  • Supplement Electrolytes (if symptoms present)
  • Weight
  • Blood pressure

Every 3–6 months:

  • HbA1c (if diabetic)
  • HOMA-IR
  • Lipids, including Apo B 
  • Kidney function
  • Medication review

Tailor monitoring to each patient’s risk level.

Common short-term effects (‘keto-flu’)

  • Headache
  • Fatigue
  • Lightheadedness
  • Constipation
  • Muscle cramps
  • Poor sleep
  • Irritability.

Management

  • Salt is very important. Many need up to two teaspoons a day. Add this to a drink bottle and sip throughout the day. Check blood pressure after adding extra salt. Adding salt to food is often not adequate. Some suggest just two salty OXO cubes a day.
  • Add magnesium 
  • Encourage gradual carb reduction

Serious but rare events

  • Severe dehydration
  • Electrolyte disturbance
  • Euglycemic ketoacidosis (only in SGLT2 users or type 1 diabetes with inadequate insulin dosing)

Choose based on patient goals, activity level, medications, and preferences:

  • Ketogenic: <20–50 g/day
  • Low-carb (moderate): 50–130 g/day

Start with an initial target based on the individual’s goals, health status, and lifestyle, and then adjust it over time based on the results and tolerability.

Protein sources (include at every meal):

  • Eggs and dairy
  • Tofu, tempeh, seitan
  • Legumes (in moderation—they’re high in starch)
  • Nuts and seeds

Healthy fats:

  • Avocado
  • Olive oil
  • Nuts and seeds
  • Cream 
  • Avocado oil
  • Coconut oil 

Key considerations:

  • Eat plenty of non-starchy vegetables for fibre and vitamins
  • Aim for 1–1.2 g/kg body weight of protein per day
  • Monitor iron and B12 if limiting animal products
  • Whole, minimally processed foods
  • Non-starchy vegetables
  • Adequate protein
  • Healthy fats
  • Limited refined carbs and sugars
  • Focus on sustainability and food quality.

Typical effects:

  • Triglycerides decrease
  • HDL (“good”) cholesterol increases
  • LDL cholesterol is unpredictable—it may rise, especially in lean, physically active people. In obese and those with diabetes LDL- C generally stays the same.
  • Blood pressure may decrease
  • Weight loss can increase LDL-C, so always wait until weight is stable before taking any action.

Overall cardiovascular risk depends on many factors, including:

  • Weight and waist circumference
  • Blood pressure
  • Blood sugar and insulin sensitivity
  • Inflammatory markers
  • Lipid response

Clinician action: 

  • Monitor lipids, be aware that with rapid weight loss, LDL-C will rise, so this needs to be remeasured once weight is stable. Increasing carbohydrates can lower LDL-C.
  • A coronary artery calcium score can be reassuring if zero.
  • Measuring Apo B from baseline can help, as often it does not rise in those with metabolic syndrome. 

Quick reference: Side effects and solutions

  • “Keto flu”: Fluids, salt, slow carb reduction,
  • Constipation: salt, hydration, fibre (like psyllium husks), magnesium citrate or oxide, MCT oil or high-dose vitamin C. 
  • Low blood sugar: Reduce insulin/sulfonylureas and monitor closely
  • Ketoacidosis risk: Watch for euglycemic DKA in SGLT2 users; follow sick-day rules.

References for further reading