Dietary carbohydrate rather than protein intake drives colonic microbial fermentation during weight loss

S W Gratz* (Corresponding Author), S Hazim, A J Richardson, L Scobbie, A M Johnstone, C Fyfe, G Holtrop, G E Lobley, W R Russell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)
10 Downloads (Pure)


High protein weight loss diets are effective in aiding body weight management. However, high protein and low carbohydrate intakes can alter colonic fermentation profiles in humans and may impact on colonic health. This study aims to identify the most important dietary contributors to colonic fermentation during diet-controlled weight loss.

Overweight or obese male volunteers (n = 18) consumed a body weight maintenance diet (fed at 1.5× basic metabolic rate, BMR) followed by three weight loss diets (fed at 1× BMR) for 10 days each in a cross-over design. Weight loss diets were designed as normal protein (NPWL, 15% of energy from protein, 55% from carbohydrate), normal protein enriched with free amino acids and moderate amounts of carbohydrate (NPAAWL, 15% of energy from protein, 15% from free AA, 40% from carbohydrate) or high protein containing moderate amounts of carbohydrate (HPWL, 30% of energy from protein, 40% from carbohydrate). Faecal samples collected at the end of each diet period were profiled for dietary metabolites using LC–MS/MS.

This study shows that the NPWL diet only induced very minor changes in the faecal metabolome, whereas NPAAWL and HPWL diets decreased carbohydrate-related metabolites (butyrate, ferulic acid) and increased protein-related metabolites. Most faecal metabolites were correlated with dietary carbohydrate and not protein intake.

This study demonstrates that dietary carbohydrate is the main driver of colonic fermentation in humans and that a balance between dietary carbohydrate and protein should be maintained when designing safe, effective and healthy weight loss diets.
Original languageEnglish
Pages (from-to)1147-1158
Number of pages12
JournalEuropean Journal of Nutrition
Issue number3
Early online date20 Feb 2018
Publication statusPublished - Apr 2019

Bibliographical note

This study was funded by the Rural and Environment Science and Analytical Services Division (RESAS) of the Scottish Government
Open access via Springer Compact Agreement


  • faecal metabolome
  • ferulic acid
  • butyrate
  • fermentation
  • amino acids
  • dietary fibre
  • Faecal metabolome
  • Amino acids
  • Dietary fibre
  • Fermentation
  • Butyrate
  • Ferulic acid
  • GUT


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