In the JournalsPerspective

High-fat diet linked to unfavorable gut microbiota changes

Eating a diet high in fat and low in carbohydrates can lead to changes in the gut at the microbiome level that could lead to the development of metabolic disorders, according to study results published in Gut.

Duo Li, PhD, of the Institute of Nutrition and Health at Qingdao University in China, and colleagues wrote that their findings could be important in countries where diets are becoming more westernized.

“Western-type diet has a strong effect on the genetic composition and metabolic activity of gut microbiota,” they wrote. “Evidence has shown that in humans gut microbiota diversity and richness are reduced when comparing such high-fat diets with more traditional diets with relatively higher proportions of carbohydrate. Such diet-induced ‘dysbiosis’ in gut-associated microbial communities has been postulated as a major trigger of metabolic impairments associated with obesity.”

Researchers conducted a 6-month randomized controlled-feeding trial comprising 217 healthy young adults (aged 18-25 years; 52% women; BMI <28 kg/m²). They randomly assigned patients to go on one of three isocaloric diets (lower-fat [fat 20% energy], moderate-fat [fat 30% energy] and higher-fat [fat 40% energy]) and assessed the effects of the dietary interventions on the gut microbiota and inflammatory triggers in blood and fecal samples taken at baseline and after 6 months.

Investigators found that the lower-fat diet was associated with increased alpha-diversity assessed by the Shannon index (P = .03), as well as increased abundance of Blautia (P = .007) and Faecalibacterium (P = .04). The higher-fat diet was associated with increased levels of Alistipes (P = .04) and Bacteroides (P < .001) with decreased levels of Faecalibacterium.

Li and colleagues found that the higher-fat diet was associated with changes to long-chain fatty acid metabolism, which resulted in higher levels of chemicals that could potentially trigger inflammation.

“Compared with a lower fat diet, long-term consumption of a higher fat diet appears to be undesirable ... for young healthy adults whose diet is in transition from the traditionally consumed lower fat, higher carbohydrate diet to one characterized by an appreciably higher fat content,” they wrote. “These findings might also have relevance in developed countries in which fat intake is already high.” – by Alex Young

Disclosures: The authors report no relevant financial disclosures.

Eating a diet high in fat and low in carbohydrates can lead to changes in the gut at the microbiome level that could lead to the development of metabolic disorders, according to study results published in Gut.

Duo Li, PhD, of the Institute of Nutrition and Health at Qingdao University in China, and colleagues wrote that their findings could be important in countries where diets are becoming more westernized.

“Western-type diet has a strong effect on the genetic composition and metabolic activity of gut microbiota,” they wrote. “Evidence has shown that in humans gut microbiota diversity and richness are reduced when comparing such high-fat diets with more traditional diets with relatively higher proportions of carbohydrate. Such diet-induced ‘dysbiosis’ in gut-associated microbial communities has been postulated as a major trigger of metabolic impairments associated with obesity.”

Researchers conducted a 6-month randomized controlled-feeding trial comprising 217 healthy young adults (aged 18-25 years; 52% women; BMI <28 kg/m²). They randomly assigned patients to go on one of three isocaloric diets (lower-fat [fat 20% energy], moderate-fat [fat 30% energy] and higher-fat [fat 40% energy]) and assessed the effects of the dietary interventions on the gut microbiota and inflammatory triggers in blood and fecal samples taken at baseline and after 6 months.

Investigators found that the lower-fat diet was associated with increased alpha-diversity assessed by the Shannon index (P = .03), as well as increased abundance of Blautia (P = .007) and Faecalibacterium (P = .04). The higher-fat diet was associated with increased levels of Alistipes (P = .04) and Bacteroides (P < .001) with decreased levels of Faecalibacterium.

Li and colleagues found that the higher-fat diet was associated with changes to long-chain fatty acid metabolism, which resulted in higher levels of chemicals that could potentially trigger inflammation.

“Compared with a lower fat diet, long-term consumption of a higher fat diet appears to be undesirable ... for young healthy adults whose diet is in transition from the traditionally consumed lower fat, higher carbohydrate diet to one characterized by an appreciably higher fat content,” they wrote. “These findings might also have relevance in developed countries in which fat intake is already high.” – by Alex Young

Disclosures: The authors report no relevant financial disclosures.

    Perspective
    Kelly Issokson

    Kelly Issokson

    Wan and colleagues recently published their study in Gut examining the impact of fat on gut microbiota, the fecal metabolome, as well as cardiometabolic risk factors in a healthy young population living in China. The primary aim of this randomized controlled feeding trial was to determine if a low-fat diet was more effective than a high-fat diet in helping participants lose weight. Subjects were randomized into one of three isocaloric dietary interventions: low fat (20% fat, 14% protein, 66% carbohydrate), moderate fat (30% fat, 14% protein, 56% carbohydrate), and high fat (40% fat, 14% protein, 46% carbohydrate). Fiber provided in all diets was similar to baseline at 14 grams per day (low fiber). Subjects were followed for 6 months and stool was collected at baseline and at the end of the trial.

    All groups lost weight, but the low-fat group lost the most. Interestingly, the study found that the high-fat diet led to unfavorable changes in the microbiota, the metabolome as well as pro-inflammatory markers, however, it is important to note that the type of fat the researchers modified in their dietary intervention was soybean oil, rich in omega 6 fatty acids or linoleic acid (LA). The researchers found increased levels of arachidonic acid (precursors of inflammatory compounds derived from LA) in the high fat group.

    The results of this study are limited in terms of generalizability, and because the study was conducted in a young and healthy population, it is hard to say how these diet changes would affect other groups of people.

    I will continue to recommend the Mediterranean-style eating pattern, which has been associated with favorable changes in the microbiota and metabolome as well as positive effects on health and wellness. A Mediterranean diet is rich in fiber, fruits, vegetables, nuts, seeds, whole grains, legumes, olive oil (high in omega 3 fatty acids), and encourages moderate to low intake of fish, dairy, and meat.

    • Kelly Issokson, MS, RD, CNSC
    • Registered Dietitian, Nutrition and Integrative IBD Program
      Cedars-Sinai

    Disclosures: Issokson reports no relevant financial disclosures.

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