Low Carb Diets: FAQs

What are carbs? 

Carbohydrates, also referred as carbs, are one of the three main macronutrients (along with fats and proteins) and give you energy to keep you fuelled for the day.  

Carbs also contribute towards your fibre intake. Fibre plays a role in gut health (as food for your friendly gut bacteria), may help with better blood glucose control, and reduces the risk of cardiovascular disease and bowel cancer.

What are key food sources of carbs?

• Starch (found in grain-based foods such as rice, breads, pasta), some fruits and some vegetables, beans and peas)  
• Fibre (fruits, vegetables, and whole grains) 
• Sugar (Fructose in fruit, lactose in milk-based products) 
• Added sugars (also known as free sugars) are also a form of carbohydrate that is added to food (for example, cake, biscuits, ice cream) or naturally occurring sugars (honey, fruit juices and syrups) 

What counts as a 'low-carb diet'?

A ‘low carb diet' means cutting the amount of carbohydrates that you eat but not everyone is agreed on the exact amounts. Even researchers have used different definitions across the research.

Luckily the classification by Feinman et al (2015) has set some use cut offs and these are now being used widely [1] .

• Ketogenic diet = <50g per day
• Low carb = 50-130g a day

What about following the low carb diet when you have type 2 diabetes?   

According to the Science Advisory Committee on Nutrition (SACN) and Diabetes UK [2], a low-carb diet can be an effective short-term (less than 12 months) strategy for weight loss for those with type 2 diabetes. They define low carb as limiting carb intake between 50g to 130g a day.

Not everyone living with type 2 diabetes are overweight but regardless of an individual’s weight, eating less carbs improves glycaemic control [3].

What’s the difference between 'Keto' and 'Low-Carb'?    

A ketogenic diet, also known as a keto diet, is an extremely low carb and high fat dietary approach. By drastically reducing your carb intake and increasing your fat intake, the reduction in carb intake means that your body will utilise fat for energy instead – this is called ketosis. It is defined by having less than 50g of carbs a day.

Anecdotal reports from patients and the public are that it can be challenging to adhere to a keto diet on a long-term basis and so it might not be a sustainable weight loss approach.

A keto diet can be used under medical supervision for those with epilepsy and metabolic disorders. 

How about 'Low-Carb' vs. the Mediterranean Diet?    

A low carb diet may improve cardiovascular health, blood glucose control and aid weight management but it's not the only diet that has been shown to do so. The Mediterrenean Diet has been claimed as one of the best-researched backed diets and include carbs.

Based on traditional eating habit from the Mediterranean, the diet includes lots of vegetables, fruits, nuts, beans, wholegrains, seeds and olive oil. Dairy, fish, chicken and eggs are eaten in moderation and red meats consumed sparingly.

Whilst the diet does include a reasonable amount of carbs it must be underlined that these come in the form of wholegrains and from whole foods (not refined processed sources). 

Take home message... it's not just about how many carbs you eat but also what form they come in!

What are the Pros and Cons of Low-Carb Diets? 

Pros 

• Replacing refined carbs and/or ultra-processed foods with whole foods. 
• As with all dietary approaches, it increases food awareness, so it makes people think about what there are eating
• It is likely you will have added more fibre in your diet so your gut health may improve 
• It is likely that you will have adequate protein intake daily so it may help you to feel fuller for longer and reduce the food cravings 
• Short-term weight loss 
• Improved blood glucose control

Cons 

• Risk of not eating enough fibre may lead to constipation 
• Risk of not eating enough carbs to suit your daily energy requirements which may result in headaches, increased food cravings and low energy 
• Risk of meals being a bit boring and lacking in variety 
• Risk of micronutrient deficiencies if not eating a range of foods 
• Risk of an unhealthy relationship with food (e.g., over restriction and/or obsessiveness about food) 
• Risk of bad breath and/or unpleasant taste in mouth 

Important considerations for some individuals    

Certain population groups should modify their carb intake with caution. 

• Are you taking insulin? If you are using insulin, there is a risk of hypoglycaemia or in exceptional cases, diabetic ketoacidosis (DKA). Please speak to your doctor if you are taking insulin prior to trying a low carb approach.  
• Do you take hypertension medication? Please consult your doctor to inform them before starting a low-carb approach as there is a risk of low blood pressure and dizziness. 
• Are you breastfeeding? Please speak to your doctor before experimenting with low carb as the metabolic demands are slightly higher than your usual daily calorie intake 

Some Final Thoughts     

More research is needed to analyse the long-term effects of following a low carb diet and currently, there is not enough evidence to suggest that such a diet is a better intervention than other approaches for weight loss.

But as the saying goes, 'different strokes for different folks', everyone is different and different diets work differently for everyone. A personalised approach is essential – and alongside diet, physical activity levels, personal weight loss goals, lifestyle and (cultural) beliefs all play an important role in the weight loss journey [4].