High protein diets are pretty hot right now, especially for weight loss. Also, high protein, high fat diets like the ketogenic diets are gaining popularity.

Do high protein diets lead to weight loss?

Studies with mice and rats have shown good results with high protein and restricting carbohydrates in rodents, but the evidence for people is mixed. There is no consistency or conclusion for humans.

But some people do get results, they feel better with less carbs, and they lose weight, so what is the problem?

There are results from studies showing a diet high in red meat and eggs increases the amount of certain compounds (L-carnitine and phosphatidylcholine)  which can be metabolized into another compound TMAO. In humans, circulating TMAO levels are reported to be associated with increased risk for atherosclerosis development and linked to obesity. 

Studies have also shown eating very high protein diets may lead to kidney issues as the body cannot process such large amounts.

We need fibre in our diets

Fibre is in starchy carbohydrates.

When we restrict carbohydrates we starve the good bugs of their fuel. Fibre is high in whole grains, and starchy vegetables such as root veg (e.g. carrots, butternut squash, sweet potato).

We need fibre as fuel for our healthy microbes in the gut, as well as keeping our bowels moving regularly.

Fibre is good for us in two ways:

  1. High fibre foods reduce the energy density of the diet (which means we stay fuller for longer on less calories), and
  2. The bugs in our gut ferment the fibre to produce short chain fatty acids (SCFAs) and these SCFAs improve our metabolism, helping us manage our weight better.

How high protein low carb diets affect your gut health

A high-protein, low carbohydrate diet can decrease the short chain fatty acids we need, especially butyrate (which is anti-inflammatory), and a decrease in metabolites associated with protection from cancer.

This means whilst a person might lose weight quickly, their microbiome is suffering if this diet is continued over the long term.

We don’t know the long term consequences of a low carbohydrate diet with limited fibre.

People feel better when they go on a strict high protein, low carb diet often because they cut out the huge amount of bread, sweets, cakes and junk food that they normally eat.

They focus on eating more vegetables, and drinking water.

This is always going to make you feel better when you shake up your diet.

Of course a diet high in processed carbs is also very low in fibre and will result in the same issues above.

So removing processed carbohydrates (think white bread, white pasta, etc) will not negatively impact your fibre, in fact if you replace it with vegetables and healthy protein you’ll be better off than eating nutrient poor foods.

But high protein, low carb diets are hard to maintain for most people, socially as well as in everyday life.

And it’s not a balanced diet.

What is a balanced diet?

A balanced diet is different for everyone, but you need a mix of foods to make a healthy diet.

Eliminating completely whole macro food groups like carbohydrates hasn’t been proven over the long term.

Aim to include:

  • A mix healthy fats every day (oily fish, avocado, coconut / olive oil)
  • Proteins at every meal (includes pulses, tofu, nuts and seeds, as well as dairy, meat and fish)
  • Aim for 7 a day (5 vegetables and 2 fruits)
  • Aim for 8 glasses of water
  • Lots of fibre – we need a balance of fibre from whole grains and vegetables. Missing out all carbs will not give you the fibre you (and your bugs) need for health.

Hi I'm Anna Mapson, registered Nutritionist (mBANT, CNHC). I help people with IBS, SIBO, reflux and other gut health issues.

I can help you to:

  • understand your digestion better, so you recognise your triggers
  • eat a well balanced diet, with tasty meals that are simple to prepare
  • develop healthy, sustainable habits for life

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