CLA Supplement: Benefits, Dosage & Side Effects

If you’re researching a CLA supplement, you’ll see bold claims about fat loss and “lean muscle.” Here’s the short answer: in humans, CLA’s effects on weight and body composition are modest at best. Safety beyond six months (and in people with diabetes) isn’t established. Some studies also flag potentially adverse changes to lipid levels.

This guide distills the human evidence, safety data, dosing ranges, and practical next steps—including how to objectively track results with DEXA.

Quick answer (what most people want to know):

• Does CLA work for fat loss? Expect small, inconsistent changes at best in human trials—often too small to notice day to day (long-term RCT meta-analysis; systematic review with dose–response, 2023).
• Typical dose used in studies: ~3–6 g/day for 8–24 weeks. If you trial it, a common starting dose is ~3 g/day (2023 systematic review).
• Is it safe? Short-term use (≤6 months) looks acceptable for generally healthy adults; longer-term safety and use in type 2 diabetes are not established (EFSA 2010; EFSA 2012 update).
• Any red flags? Some evidence suggests lipoprotein(a) can rise with higher doses/longer use, and triglycerides may increase vs olive oil in some analyses (Lp(a) meta-analysis, 2021; lipids meta-analysis, 2024).
• Best way to track results: Use DEXA to measure fat, lean mass, and visceral fat every 8–12 weeks so you can see real changes beyond scale noise. Learn more: Most Accurate Body Composition Test and DEXA Scan for Visceral Fat.

What is a CLA supplement?

• CLA (conjugated linoleic acid) is a family of fatty acid isomers found naturally in dairy and beef.
• Supplements are commonly made from safflower oil and usually contain a roughly 50:50 mix of two isomers: cis-9,trans-11 and trans-10,cis-12 (overview of sources and isomers; consumer reference on CLA).

Does a CLA supplement help with weight loss or body composition?

• A long-term RCT meta-analysis (≥6 months) found small differences favoring CLA vs placebo: ~0.7 kg body weight and ~1.3 kg fat mass—likely too small to matter day to day (meta-analysis on weight and fat mass).
• A 2023 meta-analysis of 70 RCTs (n=4,159) found modest average reductions across several body composition metrics and a small increase in fat-free mass (systematic review and dose–response).
• However, when the researchers looked only at high-quality trials, the benefits for fat mass or body-fat percentage disappeared, suggesting the effects are inconsistent at best.
• Animal data are more positive than human data; human findings are mixed and may vary by isomer and health status (review of mechanisms and human data).

Potential health effects beyond weight

• Lipids: A 2024 meta-analysis of 35 RCTs reported mixed or inconsistent results—some analyses showed higher triglycerides vs olive oil and small reductions in total cholesterol vs placebo; the authors rated evidence certainty very low (systematic review and meta-analysis on lipid profiles).
• Lipoprotein(a): CLA may increase Lp(a), especially at ≥3.5 g/d over ≥6 months (meta-analysis on Lp(a)).
• Glucose/insulin: Certain isomers may worsen insulin sensitivity, particularly in at-risk populations (clinical cautions on insulin sensitivity; consumer overview).

Safety, side effects, and who should avoid it

• Common side effects: GI upset, diarrhea, nausea, fatigue, headache (side effects overview).
• Bleeding risk: CLA may slow blood clotting—stop at least two weeks before surgery and use caution with anticoagulant/antiplatelet drugs (bleeding risk details).
• Diabetes/metabolic syndrome: Human data raise concerns about insulin resistance; avoid unless advised by your clinician (clinical cautions).
• Pregnancy/breastfeeding: Avoid supplemental doses (food amounts are fine) due to insufficient safety data (safety in special populations).
• Duration: EFSA considers CLA-rich oils safe at typical intakes for up to six months in generally healthy adults; safety beyond six months or in type 2 diabetes is not established (EFSA 2010; EFSA safety opinion, 2012).

Dosage: what human studies actually use

• Diet provides roughly 15–174 mg/day of CLA—far below supplement doses (dietary intake ranges).
• Trials commonly use 3–6 g/day for 8–24 weeks. Some analyses suggest ≥3 g/day is where small effects appear, but higher-quality trials don’t show reliable fat-loss benefits (2023 systematic review; long-term analysis).
• Practical guidance: If you and your clinician decide to trial CLA, stay near 3 g/day, limit use to ≤6 months, and monitor your body composition and lipids.

Regulatory status and product quality

• In the U.S., certain CLA isomer mixtures have GRAS notices for use in specified foods (e.g., up to 3 g/serving), based on scientific procedures (FDA GRAS Notice No. 232). GRAS does not mean “proven effective” for weight loss; it only addresses safety under the intended food uses.
• In the EU, EFSA has found CLA-rich oils (roughly 80% CLA with a 1:1 mix of c9,t11 and t10,c12) safe for proposed uses for up to six months (EFSA 2010; EFSA 2012 update).
• How to choose a supplement:
  • Look for third-party testing (e.g., NSF, USP, Informed Choice).
  • Seek transparent labeling of total CLA per serving and isomer ratio.
  • Avoid proprietary blends that obscure dose.

As an independent testing company, BodySpec does not sell or endorse any specific supplement brands.

CLA vs. Other Strategies

• Building or preserving muscle: Creatine has stronger evidence for strength and lean mass than CLA. Check out our creatine dosage calculator.
• Appetite and metabolic health: Diet quality, sufficient protein and fiber, resistance training, sleep, and stress management consistently outperform any single supplement. To target the riskiest fat, focus on visceral fat reduction strategies.

FAQ

• What’s the best time to take CLA? Timing hasn’t shown a clear advantage. If you trial it, focus on a consistent daily dose and tracking outcomes. Taking CLA with meals may help reduce GI side effects like stomach upset.
• Can CLA help lower visceral fat? Human data don’t show reliable, clinically meaningful reductions. If visceral fat is your concern, prioritize nutrition + training and track with DEXA (see DEXA for visceral fat).
• How long until I see results? If any, effects are small and typically assessed over 8–12 weeks in studies (long-term meta-analysis). Use DEXA at similar intervals to check progress.

Measure Real Change with a DEXA Scan

You don’t need supplements to see meaningful change—and if you do try one, measure what matters.

• Why DEXA: It quantifies total and regional fat/lean mass and visceral fat so you can spot small, real changes. Start here: Most Accurate Body Composition Test and dive deeper into DEXA for visceral fat.
• Cadence: Re-scan every 8–12 weeks with identical prep to detect changes beyond normal measurement noise (prep and precision tips).
• Convenience: Our DEXA scans are quick and convenient, and you’ll leave with a detailed report you can act on immediately.

Ready to get your baseline? Book your BodySpec DEXA scan

Bottom line

CLA has been widely studied, but average benefits on weight and fat are small and inconsistent, and some people may see unwanted lipid changes. If you choose to try CLA, do it deliberately: limit duration, monitor lipids, and track body composition with DEXA. If you want bigger, more reliable returns, focus on training, nutrition, sleep—and consider evidence-strong supplements like creatine instead.

Disclaimer: Educational content only; not medical advice. Talk with your healthcare provider before starting any supplement, especially if you have a health condition or take medications.