Skin Tags, Acanthosis Nigricans and Insulin Resistance: What the Evidence Shows

Acanthosis nigricans is the dark, velvety, thickened skin that shows up on the back of the neck, in the armpits and in other body folds. Skin tags (acrochordons) are the small, soft, harmless growths that tend to cluster in the same places. Both are often described as skin signs of insulin resistance, and the evidence for that is real but uneven: strong and consistent for acanthosis nigricans ^{[1] [2]}, weaker and more mixed for skin tags ^{[3] [4]}. The question most people actually want answered is whether they go away when weight and insulin sensitivity improve. For acanthosis nigricans the answer is often yes ^[5]. For skin tags the evidence is thin.

The honest summary

• Acanthosis nigricans is a genuine metabolic marker. A 2026 systematic review of 656 articles found insulin resistance was the metabolic syndrome criterion most closely tied to it, and 67.4% of people with acanthosis nigricans in non-case-report studies met full criteria for metabolic syndrome ^[1].
• It carries information beyond body weight. In 1,133 young people seen in primary care, acanthosis nigricans was linked to nearly double the prevalence of type 2 diabetes (prevalence ratio 1.97) even after adjusting for age, BMI and other risk factors ^[2].
• Skin tags are a softer signal. People with at least three skin tags had more diabetes than BMI-matched controls (23.07% vs. 8.51%) ^[3], but a 2026 study of adults with overweight or obesity found skin tags did not distinguish those with prediabetes from those without ^[4].
• Acanthosis nigricans often fades after major weight loss. After sleeve gastrectomy, 86.5% of patients with obesity-related acanthosis nigricans went into remission ^[5].
• Evidence for GLP-1 drugs specifically is early. Reports of skin improvement exist ^[7], but no large trial has reported acanthosis nigricans or skin tags as an outcome.

Acanthosis nigricans: the stronger signal

Acanthosis nigricans has the better evidence base of the two. A 2026 systematic review in the American Journal of Clinical Dermatology pulled together 656 articles reporting acanthosis nigricans alongside at least one metabolic syndrome criterion ^[1]. Of all the criteria, insulin resistance showed the highest mean prevalence of acanthosis nigricans, at 72.6%. The most common pairing was insulin resistance together with raised body mass (25.5% of articles). In the subset of studies where every participant had acanthosis nigricans and the design was not a case report, 67.4% met the full definition of metabolic syndrome, and increased body mass was the most frequently reported single criterion, at 89.7%.

The more practical finding comes from a primary care study in the southwestern United States ^[2]. Clinicians examined 1,133 children and young adults aged 7 to 39. Acanthosis nigricans was present in 17% of children and 21% of adults, and the more diabetes risk factors a person had, the more likely they were to have it. After controlling for age, BMI and the number of risk factors, the prevalence ratio for type 2 diabetes in people with acanthosis nigricans was 1.97 (95% CI 1.18 to 3.27). In other words, the dark patches were not simply a stand-in for weight; they added information on top of it.

Skin tags: a real but softer signal

Skin tags are extremely common, and many people who have them are metabolically healthy. The case for them as a marker rests mostly on case-control studies. In one, 104 people with at least three skin tags were compared with 94 controls matched for age, sex and BMI, and everyone had a two-hour oral glucose tolerance test ^[3]. Diabetes was found in 23.07% of the skin tag group versus 8.51% of controls. Impaired glucose tolerance did not differ significantly (13.46% vs. 10.63%). The number of skin tags correlated with fasting glucose, and people with more than 30 skin tags had a particularly high diabetes rate, 52.0%. The number of tags did not correlate with BMI.

The counterweight is a 2026 analysis from the PREVIEW study, in which a dermatologist examined 191 adults with overweight or obesity, 151 of whom had prediabetes ^[4]. Skin tags were no more common in the prediabetes group, and skin tag counts were not associated with body weight or BMI. The one skin finding that did separate the groups was a horseshoe-shaped thickening of the sole of the foot. The fair reading is that a large number of skin tags may point toward disturbed glucose metabolism, while a few skin tags in someone who already carries extra weight tell you little on their own.

Do they fade with weight loss?

For acanthosis nigricans, the best data comes from bariatric surgery, simply because that is where large weight loss has been tracked carefully. A prospective cohort of 319 people having sleeve gastrectomy included 141 with obesity-related acanthosis nigricans ^[5]. Before surgery, that group had higher fasting glucose, higher HOMA-IR (a standard estimate of insulin resistance) and higher testosterone than patients with obesity alone. After surgery, 122 of the 141 (about 86.5%) went into remission. Skin biopsies and imaging showed the epidermis became thinner and less pigmented, and remission tracked with improvement in testosterone levels.

A smaller two-year prospective study followed 31 people with severe obesity through bariatric surgery with skin examinations at months 0, 3, 6, 12, 18 and 24 ^[6]. Acanthosis nigricans was present in 93.55% of them at the start. The authors reported improvement across many skin findings, including acanthosis nigricans and skin tags, with varied cumulative rates of improvement. They also found that 54.84% developed acute telogen effluvium, the temporary shedding of hair that often follows rapid weight loss.

That is where the evidence thins out. The skin tag finding comes from 31 patients and the abstract does not give a separate rate for skin tags. A skin tag is a physical growth rather than a change in color and texture, and existing tags usually persist unless they are removed. It is reasonable to hope that fewer new tags form as insulin resistance improves; it is not supported by good data to expect existing tags to disappear.

What this means if you are on a GLP-1

No large randomized trial of a GLP-1 medication has reported acanthosis nigricans or skin tags as an outcome. A 2025 systematic review of GLP-1 drugs and preexisting skin disease included reports of improvement in HAIR-AN syndrome, a pattern of high androgens, insulin resistance and acanthosis nigricans, along with several other conditions, with varying degrees of improvement drawn from controlled trials, cohort studies and case reports ^[7]. The authors called for larger prospective studies. So the honest position is that the mechanism makes improvement plausible, the surgical data shows it happens with large weight loss, and direct GLP-1 data is still limited.

In practice, acanthosis nigricans tends to fade gradually over months rather than weeks, because the thickened skin has to turn over. If yours improves as your weight and blood sugar improve, that is a useful visible sign that your metabolic health is moving in the right direction. If it does not, that is not a reason to worry about the treatment, but it is worth mentioning to your clinician.

Practical guidance

• Treat new acanthosis nigricans as a reason to check blood sugar. A fasting glucose or A1c test answers the question the skin raises.
• Do not scrub it. The darkening is a thickening of the skin, not dirt, and harsh scrubbing irritates it.
• Expect acanthosis nigricans to fade slowly, over months, if it improves with weight loss.
• Do not expect existing skin tags to fall off. If one bothers you or catches on clothing, a clinician can remove it simply.
• Get sudden or rapidly spreading dark patches assessed promptly, particularly with unexplained weight loss.
• Watch for hair shedding a few months into rapid weight loss. It was common after bariatric surgery and is usually temporary.