Home Ingredients ForsLean® (Coleus forskohlii / Forskolin)
Weight ManagementMen's Health

ForsLean® (Coleus forskohlii / Forskolin)

Coleus forskohlii
Evidence Level
Limited
1 Clinical Trial
3 Documented Benefits
2/5 Evidence Score

ForsLean® (Sabinsa Corporation) is a patented, standardized extract of Coleus forskohlii root providing 10% forskolin — the diterpene compound that directly activates adenylyl cyclase to elevate intracellular cyclic AMP (cAMP). Elevated cAMP is the master metabolic signaling molecule that can raise cAMP in fat, thyroid, and muscle cells in laboratory studies, though in human trials these signals have not translated into weight loss. In two double-blind human RCTs, forskolin did not reduce body weight. A single small (n=30), industry-funded trial in overweight men reported favorable body-composition changes (lower fat mass, higher lean mass); these have not been independently replicated, and a separate trial in women found no weight loss.

Studied Dose 250 mg/day ForsLean® (25 mg/day forskolin); RCTs at 250 mg twice daily (50 mg/day forskolin).
Active Compound Forskolin (coleonol, a labdane diterpene) from Coleus forskohlii Briq. root extract; standardized to 10% forskolin.

Benefits

Body-composition changes in one small men's trial (no weight loss)

A double-blind RCT in overweight men confirmed ForsLean® (250 mg twice daily) significantly increased lean body mass (+4.5 kg), reduced fat mass (-4.7 kg), and and increased bone mineral density vs. placebo, but did NOT reduce total body weight. A separate RCT in mildly overweight women found forskolin did not promote weight loss, though it may have helped mitigate weight gain vs. placebo. Both trials were small; the men's trial was industry-funded and has not been independently replicated.

Supported by Trial 1

cAMP thyroid signaling — a laboratory mechanism, not demonstrated in humans

In laboratory (in-vitro) studies, forskolin raises cAMP in thyroid cells, a pathway involved in thyroid hormone synthesis. However, human trials have not shown that oral forskolin meaningfully increases circulating thyroid hormones (T3/T4) or measured basal metabolic rate. This remains a theoretical mechanism rather than a demonstrated effect in people.

Supported by Trial 1

Testosterone support in men

The ForsLean® RCT in overweight men confirmed significant free testosterone elevation (+16.77% vs. +4.5% for placebo), attributed to cAMP-mediated activation of steroidogenic enzymes in Leydig cells. This finding comes from a single small (n=30), industry-funded trial in overweight men and has not been independently replicated. It occurred alongside body-composition changes but no reduction in body weight, and it does not apply to women.

Supported by Trial 1

Mechanism of action

1

Adenylyl cyclase activation and cAMP-mediated lipolysis

Forskolin directly activates transmembrane adenylyl cyclase enzyme, converting ATP to cyclic AMP (cAMP) in multiple cell types. In adipocytes, elevated cAMP activates hormone-sensitive lipase (HSL) through PKA phosphorylation — releasing stored triglycerides as free fatty acids for oxidation. In thyroid cells, cAMP is part of TSH receptor signaling, though oral forskolin has not been shown to raise human thyroid hormones. In Leydig cells, cAMP is involved in steroidogenesis (StAR) for testosterone biosynthesis. These are cell-level mechanisms; in human trials forskolin did not reduce body weight, and outcomes on body composition and testosterone rest on a single small men's trial.

Clinical trials

1
ForsLean® for Body Composition in Overweight Men — Double-Blind RCT
PubMed

Randomized, double-blind, placebo-controlled trial of ForsLean® (Coleus forskohlii root extract standardized to 10% forskolin, 250 mg twice daily — 50 mg total forskolin/day) vs placebo in 30 overweight men over 12 weeks. Outcomes: body composition (DXA), fat mass, lean mass, testosterone, BP. (Godard et al. 2005, Obes Res)

30 overweight men. 12-week intervention.

ForsLean® increased lean body mass, reduced fat mass, and modestly elevated free testosterone vs placebo. Critical caveat: small single trial (n=30), industry-funded (Sabinsa), and the magnitude of body composition change reported was substantial — has not been replicated in independent trials. A subsequent trial in women showed no significant body composition effects. Modern view: ForsLean® has limited and inconsistent body composition evidence.

Side effects and drug interactions

Common Potential side effects

Generally well tolerated at clinical doses
Mild tachycardia possible — cAMP elevates heart rate; monitor if cardiovascular concerns
Blood pressure reduction — cAMP causes vasodilation; monitor if on antihypertensives
Not for use during pregnancy

Important Drug interactions

Antihypertensives — additive blood pressure reduction; monitor
Beta-blockers — oppose cAMP-mediated effects; reduced efficacy of both
Anticoagulants — mild antiplatelet activity; monitor if on blood thinners
Asthma medications — cAMP bronchodilation; generally complementary but monitor

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Frequently asked questions about ForsLean® (Coleus forskohlii / Forskolin)

What is ForsLean?

ForsLean® (Sabinsa Corporation) is a patented, standardized extract of Coleus forskohlii root providing 10% forskolin — the diterpene compound that directly activates adenylyl cyclase to elevate intracellular cyclic AMP (cAMP).

What is ForsLean used for?

ForsLean is researched primarily for Weight Management and Men's Health. A double-blind RCT in overweight men confirmed ForsLean® (250 mg twice daily) significantly increased lean body mass (+4.5 kg), reduced fat mass (-4.7 kg), and and increased bone mineral density vs.

What is the recommended dosage of ForsLean?

The clinically studied dose is 250 mg/day ForsLean® (25 mg/day forskolin); RCTs at 250 mg twice daily (50 mg/day forskolin). Always follow the product label and check with a healthcare provider for personal advice.

Is ForsLean safe, and does it have side effects?

For most healthy adults, ForsLean is well tolerated at studied doses. Reported effects can include: Generally well tolerated at clinical doses Mild tachycardia possible — cAMP elevates heart rate; monitor if cardiovascular concerns It may also interact with some medications. ForsLean is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does ForsLean interact with any medications?

Possible interactions include: Antihypertensives — additive blood pressure reduction; monitor Beta-blockers — oppose cAMP-mediated effects; reduced efficacy of both If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for ForsLean?

NutraSmarts rates the evidence for ForsLean as Limited (2 out of 5). It is backed by 1 clinical trial and 2 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(2 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Godard MP, Johnson BA, Richmond SR Body composition and hormonal adaptations associated with forskolin consumption in overweight and obese men. Obes Res. 2005;13(8):1335-43. doi: 10.1038/oby.2005.162.PubMedUsed to support: Randomized, double-blind, placebo-controlled human RCT — the primary ForsLean® pivotal trial. Coleus forskohlii standardized extract (250 mg twice daily = 50 mg/day forskolin, matching ForsLean® dosing) significantly increased lean body mass, decreased body fat percentage, and elevated serum free testosterone in overweight/obese men over 12 weeks. Supports the body-composition and testosterone findings, but note the trial did NOT reduce total body weight and is a single, unreplicated, Sabinsa-funded study.
  2. Henderson S, Magu B, Rasmussen C, Lancaster S, Kerksick C, Smith P, Melton C, Cowan P, Greenwood M, Earnest C, Almada A, Milnor P, Magrans T, Bowden R, Ounpraseuth S, Thomas A, Kreider RB Effects of coleus forskohlii supplementation on body composition and hematological profiles in mildly overweight women. J Int Soc Sports Nutr. 2005;2(2):54-62. doi: 10.1186/1550-2783-2-2-54.PubMedUsed to support: Randomized, double-blind, placebo-controlled human RCT examining Coleus forskohlii supplementation body composition effects in mildly overweight women. Second published clinical trial on standardized Coleus forskohlii extract at the ForsLean® dose, extending evidence to a female population. This trial concluded forskolin does NOT appear to promote weight loss (though it may help mitigate weight gain) and found no significant body-composition benefit — a null result on the claimed outcome.