RE-COMP: Understanding Body Composition, Cellular Energy, Healthy Aging & Hormone Research
RE-COMP is an educational resource about body composition, cellular energy metabolism, healthy aging, growth-hormone physiology, and current research involving NAD and Sermorelin.
Body composition describes the relative amounts of fat, lean tissue, bone, and other components of the body. Body composition changes throughout life and can be influenced by nutrition, physical activity, age, genetics, sleep, hormones, medications, health conditions, and energy balance.
Researchers also study cellular metabolism and hormonal signaling to better understand how these systems change with age.
NAD and Sermorelin are associated with very different biological pathways and should not be interpreted as an established combination for changing body composition, preventing aging, or increasing lifespan.
Understanding Body Composition
Body composition is influenced by multiple interacting biological and lifestyle factors.
These can include:
Weight change ≠ composition change:
Changes in body weight do not necessarily reflect equivalent changes in body composition. For example, changes in weight can involve fat mass, lean tissue, body water, or combinations of these components. Maintaining muscle through appropriate nutrition and resistance exercise can be particularly important as people age.
Understanding NAD
Nicotinamide adenine dinucleotide (NAD⁺) is a molecule found throughout the body's cells. It plays essential roles in:
Because NAD biology is connected to cellular metabolism, researchers have investigated changes in NAD metabolism during aging and disease. However, the relationship between NAD and human aging is more complicated than is sometimes suggested in wellness marketing.
A 2025 review concluded that evidence demonstrating an age-related decline in NAD⁺ in humans has been consistent in only a limited number of studies, and human clinical trials involving NAD precursors have demonstrated limited efficacy. PubMed
A 2026 study examining seven independent human cohorts found that whole-blood NAD⁺ remained remarkably stable with age, challenging its use as a straightforward biomarker of aging. PubMed
NAD & Healthy Aging Research
NAD-related research has attracted significant interest because of NAD's fundamental roles in metabolism and cellular biology. Much of the early evidence supporting NAD-targeted approaches came from laboratory and animal research.
Human studies have more commonly investigated NAD precursors, such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), rather than administration of NAD⁺ itself.
A 2026 systematic review identified 33 human intervention studies and found that oral NR and NMN generally increased NAD-related biomarkers. However, effects on metabolic, vascular, functional, and other healthspan-related outcomes were heterogeneous and frequently absent or limited to particular endpoints. PubMed
The review found no eligible clinical outcomes trials evaluating intravenous or intramuscular NAD⁺ itself for anti-aging or wellness indications. PubMed
Biomarker ≠ clinical benefit:
Increasing an NAD-related biomarker should not automatically be interpreted as demonstrating improved longevity or clinically meaningful anti-aging effects.
NAD & Body Composition
Researchers have also investigated whether interventions affecting NAD metabolism influence metabolic health and physical function. Preclinical studies have generated considerable interest, but translation into humans remains uncertain.
For example, a randomized controlled trial of the NAD precursor NMN in older men found increased blood NAD-related concentrations and exploratory changes in some measures of physical function, but no significant effect on body composition. PubMed
Research involving NAD precursors should not automatically be used to make conclusions about administering NAD itself.
The specific compound, formulation, dose, route of administration, population, and clinical outcome all matter when interpreting the evidence.
Understanding Sermorelin
Sermorelin is a synthetic peptide corresponding to a portion of naturally occurring growth hormone-releasing hormone (GHRH). GHRH is produced in the hypothalamus and signals the pituitary gland to release growth hormone.
Growth hormone secretion occurs naturally in pulses and is influenced by:
Growth hormone also influences production of insulin-like growth factor 1 (IGF-1). The GH/IGF-1 pathway participates in normal growth, metabolism, tissue maintenance, and body-composition physiology.
However, involvement of a biological pathway in body composition does not establish that increasing activity within that pathway will safely produce beneficial body-composition or longevity outcomes.
Sermorelin & Body Composition Research
Sermorelin has historically been studied for its ability to stimulate endogenous growth-hormone secretion. This makes its biology different from directly administering growth hormone.
Research into the GH/IGF-1 system has examined relationships involving:These physiological relationships should not be interpreted as proof that Sermorelin improves body composition or extends longevity in otherwise healthy adults.
Evidence demonstrating a change in GH or IGF-1 is also not equivalent to demonstrating a clinically meaningful improvement in strength, physical performance, healthspan, or lifespan.
Understanding Healthy Aging & Longevity
Healthy aging and longevity are not interchangeable concepts. Longevity refers to length of life. Healthspan generally refers to the period of life spent in relatively good health.
Scientists study many biological processes associated with aging, including:No single biomarker or biological pathway fully determines how a person ages.
Research involving NAD metabolism or growth-hormone signaling should therefore not be interpreted as demonstrating that NAD or Sermorelin slows, stops, or reverses human aging. Current reviews of NAD-targeted interventions continue to emphasize substantial uncertainty about their therapeutic value for human aging. PubMed
Understanding the Evidence
Research involving NAD and Sermorelin represents different areas of biomedical science.
NAD research includes:
- Cellular studies
- Animal studies
- Human metabolic studies
- NAD-precursor clinical trials
- Biomarker research
- Aging research
Sermorelin research relates primarily to:
- Growth-hormone physiology
- GHRH signaling
- Pituitary function
- GH/IGF-1 biology
Research demonstrating a biological mechanism does not necessarily establish a clinically meaningful health benefit.
Likewise, increases in NAD-related metabolites, growth hormone, or IGF-1 should not automatically be interpreted as evidence of improved body composition, slower aging, or increased lifespan. Large, appropriately controlled human studies using clinically meaningful outcomes are needed to establish those conclusions.
Supporting Healthy Body Composition & Aging
Established approaches supporting body composition and healthy aging can include:
Individual needs vary according to age, health, medications, physical ability, and medical history.
Regulatory & Safety Considerations
The regulatory status of NAD deserves particular attention.
As of FDA's April 22, 2026 update, Nicotinamide Adenine Dinucleotide (NAD) appears in 503A Category 1 — Bulk Drug Substances Under Evaluation. That classification should not be confused with FDA approval of NAD as a drug for body composition, anti-aging, or longevity. U.S. Food and Drug Administration
FDA has also warned specifically about injectable NAD⁺ products. The agency reports receiving adverse-event reports following injectable NAD⁺, including severe chills, shaking, vomiting, and fatigue, with some patients requiring medical treatment. FDA stated that these reactions were consistent with excessive endotoxin levels and reminded compounders to use ingredients suitable for sterile compounding. U.S. Food and Drug Administration
FDA also issued a January 2026 warning letter involving an outsourcing facility that compounded NAD⁺ products under circumstances FDA said did not meet conditions for the applicable 503B exemptions. U.S. Food and Drug Administration
These distinctions matter because being studied, being used in compounding, appearing on an FDA compounding-category list, and being FDA-approved are not the same thing.
The regulatory status, formulation, route of administration, source, sterility, and quality of a compounded product can all be important considerations.
Questions to Discuss With a Healthcare Professional
Patients learning about body composition, NAD, Sermorelin, and healthy-aging research may wish to ask:
Continuing Research
NAD metabolism and growth-hormone physiology remain active areas of biomedical research.
Future research may clarify which populations, if any, benefit from specific NAD-targeted or growth-hormone-related interventions. Patients should distinguish among normal physiology, biological mechanisms, biomarkers, experimental research, compounded preparations, and established FDA-approved medical treatments when evaluating claims about body composition and longevity.
Educational Resources & Citations
This page is provided for general educational purposes only. It is not intended to provide medical advice, diagnosis, or treatment.
References to NAD, Sermorelin, growth hormone, IGF-1, body composition, longevity, cellular metabolism, biological mechanisms, laboratory research, animal studies, or areas of clinical investigation are provided for educational purposes and should not be interpreted as a recommendation or endorsement of a particular substance or treatment.
Discussion of NAD or Sermorelin does not establish that either substance, individually or in combination, has been demonstrated to improve body composition, extend lifespan, slow aging, reverse aging, or improve longevity.
Changes in biomarkers such as NAD-related metabolites, growth hormone, or IGF-1 should not automatically be interpreted as clinically meaningful improvements in health or longevity.
Treatment decisions should be individualized and made with an appropriately licensed healthcare professional based on medical history, current health, medications, potential risks, available clinical evidence, and professional clinical judgment.
FDA approval status, compounding policies, clinical evidence, and regulatory requirements may change. Current information should be verified through the U.S. Food & Drug Administration and other recognized medical resources.