high fat diet
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A recently published study has assessed the effects of overfeeding with a high-fat diet on insulin sensitivity, gut barrier function, and fecal microbiota in humans.

A Western diet is typically described as being high in energy density, with a large fat and carbohydrate content. Within the last ten years, gut microbiota and impaired gut barrier functionality have been considered as possible risk factors for low-level inflammation. Past research has demonstrated that high-fat diets can cause changes to gut bacteria within mice. Additional studies in humans have shown that a high-fat diet of four to eight weeks can increase gut permeability which can lead to the movement of gut bacteria from the gut mucosa to other, usually sterile, tissues. Thus, increased gut permeability is associated with many diseases including celiac disease and inflammatory bowel disease.

Despite this past research work, it remained uncertain whether short-term overfeeding affects gut permeability.  This led researchers to carry out a study to investigate the effects of short-term over-feeding on insulin sensitivity, gut permeability, and microbiota formation.

This recent prospective intervention study published in The Journal of Nutrition and Disease was carried out on 24 healthy men who were given a high-fat diet by the addition of 1000 calories a day (as whipping cream) above their energy expenditure over a period of seven days.

During the study, gut permeability, insulin sensitivity, and gut microbiota profiles were assessed before and after overfeeding and for 14 days after. The results of the study showed that the participants gained approximately 1kg in body weight, and overfeeding was not associated with a major change in insulin sensitivity.

However, overfeeding for the duration of seven days did result in elevated serum LDL, HDL, and cholesterol levels. The markers assessed for gut permeability during the study remained unaltered. In addition, overfeeding during this study was not associated with changes in gut microbiota for the majority but some marked changes were observed in a subgroup of six participants.

The findings of this study suggest that acute overfeeding with a high-fat diet does not significantly affect gut permeability and insulin sensitivity in normal-weight men, and changes in fecal bacteria were only seen in certain individuals during the study.

The main limitation of this study is the short duration of overfeeding, being only seven days, which means the effects of long-term overfeeding cannot be ruled out. In addition to this, certain fatty acids were not investigated during this study such as the n-3 fatty acids, which are known to affect inflammation.

Further research is required in order to assess the long-term effects of overfeeding, the effects of certain fatty acids on inflammation and the variation between individual responses to dietary changes.

Written by Jade Marie Evans, MPharm, Medical Writer

Reference: Ott.B et al. (2018). Short-Term Overfeeding with Dairy Cream Does Not Modify Gut Permeability, the Fecal Microbiota, or Glucose Metabolism in Young Healthy Men. Available: https://www.ncbi.nlm.nih.gov/pubmed/29378051. Last accessed 20th Feb 2018

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