CLA (Conjugated Linoleic Acid) – Body Composition and Metabolism

CLA (Conjugated Linoleic Acid) is a group of natural trans-fatty acids found primarily in dairy and meat products from ruminants. As a supplement, CLA is mainly used to improve body composition (reduction of body fat, preservation/building of muscle mass) – with moderate scientific evidence.

CLA Isomers: c9,t11 and t10,c12

CLA exists as a mixture of various geometric isomers. Two are primarily biologically active:

Isomer	Origin	Main Effect
c9,t11-CLA (Rumenic Acid)	Main isomer in food (~75–80%)	Anticarcinogenic, immunomodulatory, anti-atherogenic
t10,c12-CLA	Main isomer in supplements (~50%)	Fat reduction, insulin resistance (controversial)

Important: Supplement-CLA typically consists of an approximately 50/50 mixture of both isomers, thus differing from natural CLA in foods.

Mechanisms of Action

PPARγ Modulation: t10,c12-CLA inhibits PPARγ in fat cells → reduces lipogenesis and increases lipolysis
Apoptosis of Fat Cells: Induces programmed cell death in adipocytes
Energy Expenditure: Slight increase in basal metabolic rate
Protein Synthesis: Possibly anabolic effects on muscle tissue (via PPARδ)
Anti-inflammatory: c9,t11-CLA modulates eicosanoid synthesis

Clinical Evidence

Parameter	Effect (Meta-Analyses)	Duration
Body Fat	-0.1 kg/week on average; ~1.3 kg total reduction over study period	12+ weeks
Lean Mass	Slight increase or preservation with calorie-restricted diet	12+ weeks
Insulin Sensitivity	Contradictory – t10,c12 can increase insulin resistance in high doses	Variable
Inflammation	Moderately anti-inflammatory	Long-term

Dosage and Sources

Source	CLA Content	Note
Grass-fed beef	3–5 mg/g fat	Highest natural content
Whole milk (pasture-fed cows)	~5–7 mg/g fat	Significantly higher than stall-fed
Supplement (safflower oil-based)	75–80% CLA	Standardized to c9t11 + t10c12

Therapeutic Dosage: 3–6 g/day; effects on body composition usually visible at 4–6 g/day. Take with meals (improves tolerance).

Frequently Asked Questions (FAQ)

Is CLA suitable for vegans?

Standard CLA supplements are made from safflower oil and are plant-based – therefore vegan. Natural CLA sources, however, are animal-based.

Are there risks with CLA supplementation?

At high doses (>6 g/day), increased insulin resistance, increased oxidation markers (lipid peroxidation), and slight liver fat accumulation have been reported. At recommended doses (3–4 g/day), CLA is considered safe.

CLA or L-Carnitine for fat loss?

Both have moderate effects on body fat with different mechanisms. CLA: Directly influences fat cell metabolism. L-Carnitine: Improves fatty acid transport. Can be combined, but no substitute for a calorie deficit and exercise.