The Hunger Hormone: How a Genetics Discovery Rewrote the Science of Obesity

The groundbreaking discovery of leptin that earned Dr. Jeffrey Friedman the prestigious Albany Prize

Albany Prize Winner

Genetic Discovery

Medical Breakthrough

Introduction: A Paradigm-Shifting Prize

In the world of biomedical research, few honors carry the prestige of the Albany Medical Center Prize in Medicine and Biomedical Research—one of the largest awards in science and medicine in the United States, often considered second only to the Nobel Prize in Physiology or Medicine. When the 2025 recipient was announced, it celebrated a discovery that fundamentally transformed our understanding of one of humanity's most persistent health challenges: obesity.

The winner, Dr. Jeffrey M. Friedman, a scientist from The Rockefeller University, was honored for his groundbreaking discovery of leptin, a hormone that has rewritten the biological explanation for why some people struggle with their weight.

His research conclusively demonstrated that obesity has profound biological underpinnings rather than resulting primarily from a lack of willpower—a finding that has reshaped both medical treatment and social understanding of this complex condition 1 5 .

This article explores Friedman's landmark discovery, the ingenious experiments that revealed leptin's role in regulating appetite, and the powerful genetic tools that continue to drive such transformative science forward.

The Albany Prize: Celebrating Biomedical Transformations

Established in 2001 through the extraordinary generosity of the late Morris "Marty" Silverman and his Dorothy Silverman Foundation, the Albany Prize represents a $500,000 award presented annually to those whose work has demonstrated exceptional medical value of national or international importance 7 .

$500,000 Award

One of the largest prizes in medicine and science in the United States

What makes this prize distinctive is its emphasis on research that translates "from the bench to the bedside"—fundamental scientific discoveries that ultimately result in better outcomes for patients. This criterion perfectly describes Friedman's work on leptin, which began with basic genetic research in mice and culminated in life-saving treatments for people with lipodystrophy and other metabolic disorders 1 7 .

Notable Albany Prize Recipients

CRISPR Pioneers

Emmanuelle Charpentier and Jennifer Doudna

Immunology Expert

Anthony Fauci

Cancer Researcher

James Allison

The Albany Prize has previously honored other scientific luminaries including CRISPR pioneers Emmanuelle Charpentier and Jennifer Doudna, immunology expert Anthony Fauci, and cancer immunotherapy revolutionary James Allison, placing Friedman in esteemed company of researchers whose work has fundamentally advanced medical science 7 .

The Leptin Discovery: Rewriting the Science of Obesity

For decades, prevailing societal and even medical wisdom often attributed obesity primarily to personal failing—a simple equation of eating too much and exercising too little. While diet and activity certainly play roles in weight management, this perspective ignored potential biological factors that might differ between individuals.

Before Leptin Discovery

Obesity was largely viewed as a failure of willpower with limited biological understanding.

1994

Friedman and colleagues identify the ob gene and its protein product, leptin.

Mid-1990s

Research demonstrates leptin's role as a feedback signal between fat tissue and brain.

Leptin Feedback System

Fat stores increase

Leptin production rises

Brain reduces appetite

Leptin serves as a critical feedback signal in body weight regulation

Dr. Friedman's research would fundamentally challenge this oversimplified view. His discovery emerged from investigating a strain of genetically obese mice that displayed nearly insatiable appetites and weights up to three times normal. Through meticulous genetic mapping, Friedman and his team identified that these mice carried a mutation in a gene that encoded a previously unknown hormone 1 .

He named this hormone "leptin" from the Greek word "leptos," meaning thin, and demonstrated that it functions as a crucial feedback signal between fat cells and the brain 1 5 .

How Leptin Regulates Body Weight

Leptin operates through a sophisticated biological feedback system:

Normal Leptin Function
  1. Fat cells produce leptin in proportion to their size and number
  2. Leptin travels through the bloodstream to the brain
  3. Specialized receptors in the hypothalamus detect leptin levels
  4. The brain interprets high leptin as sufficient fat stores, reducing appetite and increasing energy expenditure
  5. Low leptin signals depleted fat stores, increasing hunger and conserving energy
Leptin Deficiency

In the genetically obese mice Friedman studied, a defective leptin gene meant this crucial signal was absent. Their brains constantly perceived starvation regardless of actual fat stores, driving relentless eating and weight gain 1 .

This discovery established the first biological pathway that explained how the body regulates weight long-term, moving the scientific conversation beyond simplistic notions of willpower.

"The discovery of leptin has established a biological basis for obesity, led to a life-saving treatment for people with lipodystrophy, and opened the era of molecular exploration in the field of obesity research."

Albany Medical Center Prize Committee 1

Inside the Key Experiment: From Obese Mice to Hormone Therapy

The journey to identifying leptin represents a masterpiece of scientific deduction, combining careful observation with cutting-edge genetic techniques available in the early 1990s.

Methodology: Step-by-Step Scientific Detective Work

Experimental Process
  1. Model Selection: Researchers began with two strains of genetically obese mice—ob/ob mice (lacking leptin) and db/db mice (lacking leptin receptors)—both showing extreme obesity and type 2 diabetes symptoms 1 .
  2. Genetic Mapping: Using positional cloning techniques, Friedman's team painstakingly narrowed down the chromosomal region containing the defective gene in ob/ob mice.
  3. Gene Identification: After years of work, they identified the specific gene mutation responsible for the obese phenotype.
  4. Protein Characterization: The researchers determined that this gene coded for a protein hormone that was secreted into the bloodstream.
  5. Hormone Testing: The team produced this hormone synthetically and administered it to ob/ob mice to observe its effects.
  6. Human Correlation: Parallel studies examined whether humans with obesity showed similar hormonal disruptions.

Results and Analysis: A Transformative Treatment

The experimental results were striking and unequivocal. When ob/ob mice received injections of the newly discovered leptin hormone, their behavior and physiology transformed dramatically:

Table 1: Effects of Leptin Administration in Genetically Obese Mice
Parameter Measured Before Leptin Treatment After Leptin Treatment Change
Body Weight Up to 3x normal Significant reduction ↓ 30-40%
Food Intake Excessive consumption Normalized to typical levels ↓ 50-60%
Physical Activity Low movement Increased exploration ↑ 200-300%
Metabolic Rate Reduced energy expenditure Normalized metabolism Significant improvement

Similar dramatic results were later observed in humans with congenital leptin deficiency, confirming the hormone's critical role across species 1 .

The discovery explained why the db/db mice didn't respond to leptin—they lacked functioning receptors to detect the hormone. This completed our understanding of the signaling pathway: leptin serves as the message from fat stores to the brain, and without either the message (leptin) or the ability to receive it (receptor), the system fails, resulting in severe obesity.

Table 2: Comparison of Genetic Obesity Models
Characteristic ob/ob Mice (Leptin-Deficient) db/db Mice (Receptor-Deficient)
Genetic Defect Leptin gene mutation Leptin receptor gene mutation
Circulating Leptin Absent Very high levels
Response to Leptin Therapy Dramatic weight loss No response
Appetite Regulation Completely disrupted Completely disrupted
Human Equivalent Rare congenital leptin deficiency More common leptin resistance

The Scientist's Toolkit: Modern Genetic Research Technologies

Friedman's discovery of leptin in the 1990s relied on what were then cutting-edge genetic techniques. Today's researchers have an even more powerful arsenal of tools for probing genetic mysteries. These technologies fall into several broad categories:

Genetic Testing Methodologies

Contemporary genetic analysis employs three primary approaches to detect different types of abnormalities 3 :

Cytogenetic Testing

Examines chromosome structure and abnormalities, often using techniques like fluorescent in situ hybridization (FISH) to identify chromosomal deletions or translocations associated with specific disorders.

Biochemical Testing

Measures protein activity or metabolite levels rather than directly examining DNA, particularly useful for inborn errors of metabolism.

Molecular Testing

Directly analyzes DNA sequences to identify mutations, using methods like polymerase chain reaction (PCR) and direct sequencing.

CRISPR and Genome Engineering

The revolutionary CRISPR-Cas9 system has transformed genetic research by enabling precise editing of DNA sequences. This technology allows scientists to create targeted mutations, correct genetic defects, and study gene function with unprecedented accuracy 9 .

CRISPR Resources from the Innovative Genomics Institute
  • Detailed laboratory protocols for various applications and organisms
  • Plasmids and guide RNA libraries available through repositories like Addgene
  • Bioinformatics tools for designing experiments and analyzing results

Genetically Encoded Affinity Reagents (GEARs)

A recent innovation described in Nature Communications provides researchers with a versatile new toolkit for studying protein function. The GEARs system uses short epitope tags combined with specialized binders to visualize, manipulate, or degrade specific proteins in living organisms 4 .

Table 3: Essential Tools in the Modern Genetics Laboratory
Tool Category Examples Primary Applications
Gene Editing CRISPR-Cas9, TALENs, ZFNs Targeted genome modification, gene knockout, gene correction
Gene Analysis PCR, DNA sequencing, microarrays Mutation detection, gene expression profiling, genetic mapping
Visualization GEARs, fluorescent proteins, FISH Protein localization, tracking gene expression, chromosome analysis
Bioinformatics GATK, CRISPResso, MAGeCK Sequencing data analysis, guide RNA design, screen interpretation
Data Resources ClinVar, GenomeCRISPR, ClinicalTrials.gov Variant interpretation, experimental design, clinical context

This approach offers several advantages over traditional methods 4 :

  • Small epitope tags integrate more easily into genomes than large fluorescent proteins
  • Multifunctional applications including visualization, degradation, and interaction mapping
  • Broad compatibility across model organisms from zebrafish to mice

Conclusion: From Discovery to Future Horizons

The journey from Friedman's initial observations of obese mice to the development of leptin therapies exemplifies the transformative power of basic genetic research. His work, recognized by the 2025 Albany Prize, not only provided a new biological framework for understanding obesity but also opened entirely new avenues for treating metabolic diseases.

Shifting Perspectives

Perhaps just as importantly, the leptin discovery has helped shift cultural perceptions of obesity, offering scientific evidence that weight regulation involves complex biological systems far beyond conscious control. This has helped reduce stigma while directing research toward more effective, biologically-based interventions.

Future Directions

Today's genetic researchers continue to build on this foundation, armed with increasingly sophisticated tools like CRISPR and GEARs that accelerate the pace of discovery. As these technologies advance, they promise further breakthroughs in understanding and treating not just obesity but thousands of genetic conditions that affect human health.

The Albany Prize celebrates precisely this kind of scientific journey—from fundamental questions asked in the laboratory to real-world impacts that improve human health. As Friedman's work demonstrates, sometimes the most profound medical advances begin with curious observations in seemingly specialized model systems, reminding us that basic science truly forms the foundation of medical progress.

The discovery of leptin has established a biological basis for obesity, led to a life-saving treatment for people with lipodystrophy, and opened the era of molecular exploration in the field of obesity research.

— Albany Medical Center Prize Committee 1

References