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Microbes & Immunity Management of obesity

of MCP-1 in adipose tissue has been established as triggers excessive insulin production, leading to increased
associated with heightened macrophage infiltration in adiposity and the inhibition of energy release from
rodents. Significantly, SCFAs serve as a crucial link adipose tissue. Post-prandial energy substrate deficiency
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between inflammatory reactions and the gut microbiota, in the bloodstream is detected by the hypothalamus,
demonstrating strong anti-inflammatory characteristics, stimulating appetite and reducing energy expenditure,
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particularly butyrate. Butyrate safeguards the gut against potentially resulting in a positive energy balance due to
inflammation by inducing IL-18 production and facilitating hyperphagia. Excessive consumption of UPFs can affect
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the development of regulatory IL-10-producing T cells gut flora and has been associated with a higher incidence
and T cells through GPR109a. 32,77 Moreover, butyrate can of obesity, metabolic syndrome, hypercholesterolemia,
upregulate peroxisome proliferator-activated receptor and hypertension. Diets high in protein and fat are
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gamma, enhance the production of anti-inflammatory typically linked to Bacteroides-dominant (enterotype I)
cytokines, and inhibit NF-κB activation triggered by LPS, microbiota, while high-carbohydrate diets are associated
thereby demonstrating its anti-inflammatory effects. 78,79 with Prevotella-driven (enterotype II) microbiota profiles.
The genera Fusobacterium, Pseudomonas, Escherichia- This aligns with the findings of Wu et al., who reported
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Shigella, and Campylobacter are commonly associated with that Bacteroidetes and Actinobacteria positively correlate
obesity. 80,81 LPS from members of the Desulfovibrionaceae with dietary fat and negatively with dietary fiber, while
and Enterobacteriaceae families exhibit endotoxin Firmicutes and Proteobacteria show the opposite trend.
activity that is 1,000-fold greater than that of LPS from Conversely, Brinkworth et al. found that high-fat/
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Bacteroideaceae. 82 low-fiber diets reduced the abundance of Bifidobacteria
compared to low-fat/high-fiber diets. Lower carbohydrate
12. Effects of diet on obesity and fiber intake resulted in a decline in bacteria, such as

The composition of the gut microbiota is significantly Eubacterium rectale, Roseburia spp., and Bifidobacterium
influenced by dietary habits. A diet rich in fats and sugars, spp. in obese adults. Dietary fiber increased the
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characteristic of Western cuisine, increases the relative abundance of Prevotella, whereas bile-resistant taxa, such
prevalence of Firmicutes while diminishing Bacteroidetes as Bilophila and Bacteroides were associated with high-fat,
in animal models. Furthermore, transitioning from animal-based diets. 95
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a low-fat, plant polysaccharide-rich diet to a high-fat/ Vegetarians generally exhibit greater bacterial diversity,
high-sugar “Western” diet can alter microbiota formation higher Prevotella to Bacteroides ratios, and reduced levels
within a single day in gnotobiotic mice colonized with of Enterobacteriaceae, including E. coli, compared to
human fecal bacteria. The nature of diet, combined omnivores. Moreover, vegetarians and vegans show a
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with elevated caloric intake along with reduced physical greater abundance of Lachnospiraceae (e.g., Roseburia,
activity, is among the principal factors contributing to the Anaerostipes, Blautia genera) and Ruminococcaceae
rising incidence of obesity. The origins and progression (e.g., Ruminococcus and F. prauznitzii genera), along with
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of obesity can be explained by the carbohydrate-insulin a reduced presence of Bacteroides, Parabacteroides, and
model and/or the energy balance model (EBM). The EBM Alistipes. 97
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model posits that the brain, particularly the hypothalamus,
regulates body weight by controlling food intake through The Western-style diet, marked by a high intake of
complex internal endocrine, metabolic, and neural signals protein and fats (particularly saturated fats), is associated
from peripheral organs, as well as external cues from the with an increased prevalence of metabolic disorders, such
food environment. The increased availability of ultra- as type 2 diabetes, cardiovascular diseases, and obesity. It
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processed foods (UPFs), characterized by high energy also correlates with increased abundances of Bacteroides,
density and elevated levels of fat and sugar, but low in Alistipes, and Bilophila, and decreased levels of Lactobacillus,
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protein, fiber, vitamins, and minerals, may result in a Roseburia, Eubacterium, and Enterococcus genera. In
positive energy balance and fat accumulation (adiposity), contrast, the Mediterranean diet – rich in dietary fiber from
regardless of the diet’s macronutrient composition. Typical cereals, vegetables, legumes, nuts, and fruits; unsaturated
examples of UPFs include refined cereals, sweet and fatty acids from fish and vegetable oils; and antioxidants,
savory snacks, margarine, reconstituted and ready-to-eat such as flavonoids and polyphenols – enhances overall
frozen meals, and carbonated and alcoholic beverages. microbial diversity. This includes increases in families,
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The carbohydrate-insulin model emphasizes diet quality, such as Clostridiaceae and Lactobacillaceae, and genera,
namely, chemical composition, over quantity. UPFs and such as Bacteroides, Prevotella, Bifidobacterium, Roseburia,
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other refined products are high in sugars, which elevate Lactobacillus, Clostridium, and Faecalibacterium (Table 2),
both glycemic index and glycemic load. Elevated glycemia while reducing the abundance of Proteobacteria. 101

Volume 2 Issue 4 (2025) 51 doi: 10.36922/MI025160036