Does milk thistle help with weight? What the research does and doesn't show

The evidence doesn't support milk thistle, by itself, as a weight-loss aid. The largest pooled analysis of silymarin trials to date — 33 trials, nearly 2,000 people — found no significant difference in body weight or BMI between people taking silymarin and those who weren't, even though the same trials found effects on some other metabolic markers.

What the evidence doesn't support

It doesn't support milk thistle or silymarin as something that makes you lose weight, reduce body fat, or change BMI — the largest available pooled analysis found no significant difference on either measure. It doesn't support "milk thistle for weight loss" as a general-population claim; every trial in the research below was run in adults with an existing metabolic condition like type 2 diabetes, not a healthy population trying to lose weight. None of it describes a specific brand's dose or product, and nothing here is a claim about any product.

What the trials found

A 2024 systematic review and dose-response meta-analysis in Antioxidants pooled 33 controlled trials of silymarin, 1,943 participants total, and specifically measured body weight and BMI as two of several outcomes. Across the pooled trials, there was no significant difference in either measure between the silymarin and control groups. The same analysis did find fasting blood glucose, fasting insulin, HbA1c, total cholesterol, triglycerides and LDL fell significantly more with silymarin than with placebo, and diastolic blood pressure dropped modestly — real findings, but on blood markers, not on weight itself. Those findings are covered in more detail in milk thistle and cholesterol: what the research shows.

A separate, longer trial complicates the picture rather than clarifying it. A 52-week placebo-controlled trial in 136 obese adults with type 2 diabetes tested a combination product containing both berberine (from Berberis aristata) and silymarin — the two were combined specifically because silymarin was thought to improve berberine's poor oral absorption. That combination group saw a significant reduction in BMI, waist circumference and abdominal fat (measured by bioelectrical impedance) compared with placebo, alongside improvements in blood sugar and cholesterol markers. It's a real result, but it's a two-ingredient product, and berberine on its own has separately documented metabolic effects — the trial can't tell you how much of the abdominal-fat reduction, if any, came from the silymarin rather than the berberine.

Trial	Population	Intervention	Weight/fat result
Mohammadi 2024 (33 pooled trials, n=1,943)	Adults with cardiometabolic risk factors	Silymarin alone	No significant change in body weight or BMI
Guarino 2017 (n=136)	Obese adults with type 2 diabetes	Berberine + silymarin combination, 52 weeks	Reduced BMI, waist circumference and abdominal fat vs. placebo — not attributable to silymarin alone

Questions people ask

Can milk thistle help with weight loss?

The largest pooled analysis — 33 trials, nearly 2,000 people — found no significant difference in body weight or BMI between silymarin and placebo groups. A separate, longer trial found weight and abdominal-fat reductions, but only as part of a combination product with berberine, so that result isn't evidence for milk thistle by itself.

Does taking milk thistle make you lose weight?

No trial has shown that. The largest analysis found no significant weight difference with silymarin alone.

What about milk thistle with berberine for weight loss?

One 52-week trial found a combination berberine-and-silymarin product reduced BMI and abdominal fat in obese adults with type 2 diabetes versus placebo. Because it's a two-ingredient product and berberine has its own documented metabolic effects, the trial doesn't isolate what milk thistle contributed, if anything.

Does milk thistle cause weight gain instead?

An NIH reference review notes breastfeeding mothers taking milk thistle for milk supply occasionally reported weight gain as a side effect, but that's a small, specific population, not a general finding. The larger 33-trial pooled analysis found no significant weight change in either direction. See milk thistle side effects for more.

When to talk to a doctor

Milk thistle is not a weight-loss treatment, and anyone managing obesity, type 2 diabetes or metabolic syndrome should do so with a doctor's guidance rather than relying on a supplement. If you take diabetes medication or any other prescription drug, ask a doctor before adding milk thistle — see milk thistle and medications: what to check.

Related reading: milk thistle and cholesterol: what the research shows, milk thistle benefits: what the research does and doesn't show, and what is milk thistle.