In a diet-induced obesity (DIO) study, mice or rats receive a defined higher-fat diet for a specified period.[S5] “DIO” is not a complete protocol. The strain and substrain, sex, age at diet start, diet formula, control diet, feeding duration, housing, and endpoint schedule must all be stated.
Do not describe DIO as a faithful reproduction of human obesity. Mouse and human adipose-tissue physiology differ, and a review devoted to those differences cautions that model findings require careful interpretation.[S7] The study establishes changes in the selected animal endpoints under the chosen diet. It does not establish a human metabolic phenotype or treatment effect.
Questions and endpoints
Translate the development question into a primary endpoint and a measurement schedule. The table below is a commissioning checklist, not a claim that one DIO protocol represents each listed human disease.
Study question
Protocol items to define
Body composition
Primary measure, collection schedule, fasting status, and whether food intake is measured per animal or per cage.
Glucose regulation
Assay, fasting duration, challenge route, sampling times, and analysis rule.
Circulating lipids
Analytes, fasting status, collection time, and assay method.
Liver findings
Tissue collection, histology scoring, biochemical endpoints, and whether fibrosis is expected in this exact diet-duration-strain combination.
Speakman, Hambly, Mitchell, and Król published “Animal models of obesity” in Obesity Reviews in 2007.[S5] The verified record supports the citation. Read the paper when using it to justify a specific model choice; the bibliographic record alone does not support the detailed summary in the Japanese original.
The use of animal models in diabetes research (2012)[S6]
A. J. King published “The use of animal models in diabetes research” in the British Journal of Pharmacology in 2012.[S6] The record verifies the paper, journal, and date. It does not by itself substantiate every model-use claim in the original summary.
Verified record: British Journal of Pharmacology, 2012, PMID 22352879.[S6]
More recent reviews
Of mice and men: considerations on adipose tissue physiology in animal models of obesity and human studies (2022)[S7]
Lempesis and colleagues published this review in Metabolism Open in 2022.[S7] Its stated subject is adipose-tissue physiology in obesity models and human studies, making it the relevant source here for identifying species differences rather than claiming that the model reproduces human obesity.[S7]
Animal models for type 1 and type 2 diabetes: advantages and limitations (2024)[S8]
Singh, Gholipourmalekabadi, and Shafikhani published this review in Frontiers in Endocrinology in 2024.[S8] The title frames the decision correctly: compare advantages and limitations. Do not convert that comparison into a claim that a high-fat-diet model reproduces human lifestyle disease.
Verified record: Frontiers in Endocrinology, 2024, PMID 38444587.[S8]
Examples of model components available to US sponsors
Biocytogen lists B-hGCGR mice as a human glucagon-receptor humanized model on a C57BL/6 background, with strain designation C57BL/6-Gcgr tm1(GCGR)Bcgen/Bcgen and Catalog Number 110105 (company website, accessed September 3, 2026).[S4] That record confirms model identity. It does not establish that the model or a DIO protocol is suitable for a particular test article.
Research Diets, Inc. lists formula D12492 as a rodent diet with 60 kcal% fat (company website, accessed September 3, 2026).[S3] The verified page-specific research did not establish the complete macronutrient or sucrose composition. Obtain the current formulation and select a matched control diet before finalizing the protocol.
Obtain the current composition and lot documentation; define the matched control, storage, feeding start, duration, and food-intake measurement method.
A DIO result is interpretable only in the context of its exact substrain and diet. C57BL/6J and C57BL/6N-related substrains differ in Nnt status and in metabolic responses to high-fat diet.[S1][S2] Record the full substrain rather than “C57BL/6,” and do not pool historical controls across substrains or diet formulas without justification.
Before award, require the proposal to state the animal source and substrain, sex and age, acclimation, diet catalog number and lot, matched control, feeding duration, randomization, cage-level treatment of food intake, primary endpoint, exclusions, and analysis plan. The study can establish effects in that defined system; it cannot establish efficacy or safety in patients.
References
Diet-induced obesity in two C57BL/6 substrains with intact or mutant nicotinamide nucleotide transhydrogenase (Nnt) gene. https://europepmc.org/article/MED/20057372 (accessed 2026-09-03)
Of mice and men: Considerations on adipose tissue physiology in animal models of obesity and human studies. https://europepmc.org/article/MED/36092796 (accessed 2026-09-03)
3 Recommended Contract Research Organizations
for Non-Clinical Studies
— by Target goal and Expertise
In non-clinical development, the choice of contract research organization shapes the quality of the data and the time it takes to reach the next decision. Below, three CROs are introduced by the type of study they support: pharmacology (efficacy) studies, safety studies, and pharmacokinetic (PK/PD) studies. Each summary describes the services the company offers so that you can match a provider to your target and development objective.
Pharmacology (Efficacy) StudiesDisease-Relevant Models for Translational Drug Evaluation
Reference: SMC Laboratories, Inc. official website (https://www.smccro-lab.com/)
SMC Laboratories, Inc.
SMC Laboratories is a specialized non-clinical CRO focused on in vivo pharmacology and efficacy studies using disease-relevant animal models, particularly in fibrosis, inflammation, metabolic diseases, and oncology.
Areas of Expertise
Disease-Relevant Model Portfolio
SMC Laboratories offers models covering the liver, lung, kidney, intestine, and oncology. Its portfolio includes the proprietary STAM™ model for MASH, fibrosis, and hepatocellular carcinoma.
Study Design Based on Target Biology
Study plans are developed around the target biology, mechanism of action, disease stage, and development objective. Pharmacological endpoints can be combined with histopathology, biomarkers, and disease-specific readouts.
Support from Target Validation to Proof of Concept
With experience from more than 1,000 studies for clients in 30 countries, SMC Laboratories supports programs from target validation and candidate selection through in vivo proof-of-concept studies.
Safety StudiesComprehensive Safety Assessment for Preclinical Development
Reference: Charles River Laboratories official website (https://www.criver.com/)
Charles River Laboratories
Charles River provides non-clinical toxicology and safety assessment services for programs ranging from exploratory safety studies to IND-enabling development.
Areas of Expertise
General Toxicology Across Study Designs
Services include single- and repeat-dose toxicology, dose-range finding, and general toxicology studies across multiple species and administration routes.
Non-GLP and GLP Study Support
Charles River supports both non-GLP and GLP studies, allowing sponsors to progress from early safety characterization to studies intended for regulatory submissions.
Integrated IND-Enabling Safety Assessment
Toxicology studies can be integrated with toxicokinetics, clinical pathology, histopathology, and safety pharmacology to support interpretation and IND-enabling safety packages.
Pharmacokinetic (PK/PD) StudiesConnecting Drug Exposure with Pharmacological Response
Reference: Inotiv official website (https://www.inotiv.com/)
Inotiv
Inotiv provides integrated PK/PD, DMPK, and bioanalytical services to characterize drug exposure and its relationship with pharmacological response.
Areas of Expertise
Pharmacokinetic Characterization
PK studies characterize exposure, half-life, clearance, and other pharmacokinetic parameters needed to understand how a candidate behaves in the selected model.
Exposure–Response Evaluation
Pharmacokinetic data can be combined with pharmacodynamic endpoints and bioanalysis to evaluate the relationship between drug exposure and pharmacological response.
Integrated DMPK and Development Support
Integrated DMPK, pharmacology, and safety information supports candidate comparison, dose selection, dosing-frequency optimization, and decisions about subsequent preclinical development.
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