Low carb diets: what’s the deal?

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By The Gut Health Doctor Team

Dr Megan Rossi in a lab looking through a microscope

Keto, paleo, Atkins, carnivore…they’re all popular ways to ‘do’ low carb to varying extremes. But what’s the difference and what does the science say?

I’d never recommend cutting out carbs – fibre is a type of carb that nourishes our gut microbes, so they’re not to be feared! And no, a keto diet will NOT prevent or cure #covid19.

Here’s a breakdown of what each of the ‘low carb’ diets actually means:

  • Zero carb – i.e. carnivore diet – means only eating animal products and spices.

  • Atkins diet has 4 phases, each increasing carb allowance and restricting dairy, wholegrains, starchy veg and fruit. Protein isn’t restricted and there is a plant-based version.

  • Low sugar diet restricts all sources of sugars, including fruit and dairy.

  • Paleo doesn’t have any direct limit on carbs, but limits key food groups including dairy, wholegrains and legumes.

  • Ketogenic diet means keeping high levels of ketones (a product of fat break down) in the body. To achieve this, most need to lower carbs to 20-50g/day (for context the Mediterranean diet used in my fave SMILES trial ate around 200g/day), restricting dairy, wholegrains, starchy veg, fruit and legumes, with protein making up 20% or less of your diet. Blood ketones are tested daily and there’s also modified or cyclical variations.

The science

  • There’s some evidence for a ‘lower’ carb diet for adults with type 2 diabetes, but I’d argue it’s more about carb quality (e.g. lower white rice, higher wholegrains like quinoa, freekeh etc.) than counting carbs.

  • There’s good evidence for the keto diet in some children and young people with epilepsy (under the supervision of a trained dietitian) – but 1/3 won’t see a benefit.

For the rest of us, having such a restricted diet and cutting out good quality carbs has been linked with increased irritability, constipation, low energy, low mood, bad breath and headaches. Not to mention these restrictive diets have also been shown to negatively impact our gut microbes, which do so much for us. They deserve to be nourished and nurtured, not starved and neglected.


The bottom line: eat however you want to eat, but be aware of some of the consequences of cutting out whole food groups.


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