What does obesity look like in rats? - briefly
Obese rats present pronounced subcutaneous and visceral fat accumulation, markedly enlarged abdominal circumference, and a dull, less groomed coat. Their body weight typically exceeds 120 % of the strain‑specific normal, accompanied by reduced locomotor activity and altered feeding patterns.
What does obesity look like in rats? - in detail
Obesity in laboratory rats manifests as a measurable increase in body mass accompanied by distinct morphological and physiological alterations.
Body weight typically exceeds the upper 95 percentile for the specific strain, with a rapid gain occurring after exposure to high‑calorie diets. The dorsal and ventral surfaces display pronounced adipose deposits, especially in the subcutaneous layer over the lumbar region and the inguinal area. Abdominal girth expands due to visceral fat accumulation, which can be quantified by measuring waist circumference or using imaging techniques such as magnetic resonance tomography.
Body composition analysis reveals a higher fat‑to‑lean mass ratio. Dual‑energy X‑ray absorptiometry (DXA) or quantitative magnetic resonance (QMR) consistently show fat percentages above 30 % of total body mass, compared with 10–15 % in lean controls.
Metabolic signs include hyperinsulinemia, elevated fasting glucose, and increased serum leptin and triglyceride levels. Glucose tolerance tests demonstrate delayed clearance, while insulin tolerance tests show reduced sensitivity.
Behavioral changes often involve reduced locomotor activity and increased nocturnal food intake. Open‑field assessments record lower total distance traveled and fewer rearing events, indicating diminished exploratory behavior.
Organ pathology is evident in several systems. Hepatic steatosis appears as macro‑vesicular lipid droplets within hepatocytes, detectable by histological staining (e.g., Oil Red O). Cardiac hypertrophy may be observed as increased left‑ventricular wall thickness. Adipose tissue expands through both hyperplasia (increased adipocyte number) and hypertrophy (enlarged adipocyte diameter), with crown‑like structures formed by macrophage infiltration around necrotic adipocytes.
In summary, rat obesity presents as excessive weight gain, pronounced subcutaneous and visceral fat deposits, altered body composition, metabolic dysregulation, reduced physical activity, and organ‑specific pathological changes. These characteristics provide a reproducible phenotype for experimental studies of diet‑induced obesity.