Most people dealing with acne have been told at some point that diet has nothing to do with it. That it is hormonal, genetic, or just bad luck. And while genetics and hormones are genuinely involved in acne pathophysiology, the idea that what you eat is irrelevant has not aged well. A growing body of research now makes it reasonably clear that certain dietary patterns consistently worsen acne while others consistently improve it, and the mechanisms behind these effects are well understood enough to take seriously. This is not about cutting out chocolate because your grandmother said so. This is about insulin, IGF-1, inflammation, and how the foods you eat every day are directly feeding the biological processes that drive breakouts.
How Acne Actually Develops
Before talking about diet, it helps to understand what is actually happening in the skin when acne forms. Acne develops through four key processes happening simultaneously. The sebaceous glands produce excess oil, the hair follicle lining thickens and blocks the pore, a bacteria called Cutibacterium acnes proliferates in that blocked environment, and an inflammatory response follows. All four of these processes are influenced by hormones, particularly androgens and a growth factor called IGF-1. The reason diet matters is that what you eat directly affects how much IGF-1 and insulin your body produces, and both of these compounds accelerate every one of those four processes. High insulin and high IGF-1 increase oil production, promote the thickening of follicle linings, and create an inflammatory environment that makes breakouts more frequent and more severe. Once you understand this, the dietary patterns that worsen acne start making a lot of biological sense.
The Glycemic Index Problem
The most consistently supported dietary factor in acne research is glycemic load, which is a measure of how much and how quickly a food raises your blood sugar. High glycemic load foods, things like white bread, sugary drinks, processed snacks, white rice eaten in large amounts, and confectionery, cause rapid spikes in blood glucose followed by rapid spikes in insulin. That insulin spike triggers an increase in IGF-1, which then drives sebum production and follicular changes that set the stage for acne. Multiple randomised controlled trials have shown that switching to a low glycemic load diet meaningfully reduces acne lesion counts compared to continuing a high glycemic diet. One study found that a low glycemic load diet reduced noninflammatory and inflammatory lesion counts, resulted in smaller sebaceous glands, and decreased the overall severity grading of acne over just 10 weeks. Another study demonstrated significant reductions in the free androgen index and increases in IGF-1 binding proteins, meaning less biologically active IGF-1 circulating in the body. These are not small effects from obscure studies. This is among the most replicated findings in dietary acne research.
Populations that historically had no acne, including the Kitavan islanders of Papua New Guinea and the Aché hunter-gatherers of Paraguay, were eating diets with virtually no refined grains, processed sugars, or Western processed foods. When these populations adopted Western dietary patterns, acne appeared. This does not prove causation by itself, but it aligns perfectly with what the controlled trials show about glycemic load and its downstream hormonal effects.
The Dairy Question
Dairy is the second most consistently studied dietary factor in acne, and the relationship is more nuanced than most people expect. Milk appears to be the most problematic form of dairy, and the reason has less to do with fat content than most people assume. Eighty percent of cow’s milk protein is casein, and the remaining twenty percent is whey. Whey proteins are primarily responsible for milk’s insulinotropic effect, meaning they trigger an insulin response that is disproportionately large relative to milk’s actual carbohydrate content. Casein separately stimulates IGF-1 production. Both of these effects feed the same hormonal pathway that drives acne, which is why multiple large cohort studies have found associations between milk consumption and acne prevalence in both adolescents and adults.
The distinction between different dairy products matters here. Cheese, which has a low insulin index, has not been consistently associated with acne in the research. Ice cream, which has a high insulin index due to added sugar, has. This pattern supports the insulin-mediated mechanism rather than a blanket dairy problem. For people who use whey protein supplements, the research is particularly relevant. Whey protein concentrate contains a very high proportion of leucine, an amino acid that directly activates the mTORC1 signalling pathway involved in sebum production and skin cell proliferation. Several case reports and studies have documented acne flares in young athletes after starting whey protein supplementation, with rapid clearance after discontinuing. If you are dealing with persistent acne and regularly using whey protein, that connection is worth taking seriously.
Omega-3 Fatty Acids Work in the Other Direction
While high glycemic foods and dairy tend to worsen acne through the insulin and IGF-1 pathway, omega-3 fatty acids appear to work in the opposite direction. Omega-3s reduce IGF-1 levels and inhibit the synthesis of inflammatory leukotriene B4, a compound that directly promotes the inflammatory lesions characteristic of moderate to severe acne. A randomised controlled trial found that supplementing with either an omega-3 fatty acid or gamma-linoleic acid for ten weeks significantly reduced both inflammatory and noninflammatory lesion counts compared to no supplementation. Some studies have also found that lower fish consumption is associated with greater acne severity, which is consistent with the anti-inflammatory and IGF-1-lowering effects of the omega-3s found in fish. The practical takeaway is that increasing oily fish consumption, including salmon, sardines, mackerel, and similar options, or improving the overall ratio of omega-3 to omega-6 fatty acids in your diet, supports a less inflammatory environment in the skin.
Why Your Friend Eats Everything and Never Breaks Out
This is the part of the acne conversation that population-level research cannot fully answer, and it deserves honesty rather than oversimplification. You almost certainly know someone who drinks milk daily, eats whatever they want, and has skin that has never troubled them. And you probably also know someone who is meticulous about their diet and still struggles with acne. Both of these people are real, and both experiences are valid, and neither of them cancels out the research on dietary patterns and acne.
The explanation lies in the significant individual variation in how people respond to the same dietary inputs. Genetic differences in androgen receptor sensitivity mean that the same level of IGF-1 will drive more sebum production in some people than others. Variation in the insulin response to identical meals is considerable even among healthy individuals. The density of sebaceous glands, the specific composition of the skin microbiome, baseline levels of systemic inflammation, how efficiently the liver clears IGF-1, and dozens of other factors all determine how much a dietary stimulus translates into visible skin consequences. Someone with naturally lower androgen receptor sensitivity and a robust anti-inflammatory baseline may eat a high glycemic diet for years with minimal skin consequences. Someone with the opposite profile may find that a single period of consistently poor eating is enough to trigger a flare that takes months to settle.
This individual variability is not a reason to dismiss the dietary evidence. It is a reason to treat the research as a framework for your own self-experimentation rather than a universal guarantee. The research tells you where the biological levers are. Your own skin tells you how sensitive your particular lever is. Both pieces of information matter.
How to Actually Figure Out What Is Affecting Your Skin
The most practical approach to the dietary-acne question is one that takes the research seriously as a starting point and then uses your own body as the test subject. Rather than making sweeping permanent changes based on population-level averages, structured elimination and reintroduction gives you information that is specific to you rather than borrowed from a group average.
The most logical starting point based on the evidence is liquid dairy and high glycemic foods, since these are the two categories with the most consistent mechanistic and clinical support. Try removing liquid milk and whey protein entirely for four to six weeks while simultaneously reducing your intake of processed high sugar foods, refined bread, and sugary drinks. Four to six weeks is the minimum timeframe worth committing to because skin cell turnover and acne cycle duration mean that shorter trials produce noise rather than signal. If your skin improves meaningfully during that window, you have useful information about your individual sensitivity. If it does not change at all, dairy and glycemic load are probably not your primary drivers, and you can reintroduce them without guilt while investigating other factors.
The reintroduction phase is where you get specific. Add liquid milk back in for two weeks while keeping everything else stable and observe what happens. Then remove it again and add whey back. Then experiment with glycemic load independently. This kind of sequential testing is slower and less satisfying than reading a definitive list of what to avoid, but it gives you information that a population study never can, which is how your specific biology responds to specific inputs. Some people will find that dairy is their primary trigger and glycemic load barely matters. Others will find the opposite. Some will find that neither dietary category is their main issue and the problem lies elsewhere entirely, in stress, sleep, hormonal fluctuations, or topical products. The elimination and reintroduction framework works regardless of which category turns out to be relevant for you because it generates actual evidence rather than assumptions.
What This Looks Like in Practice
Translating all of this into practical dietary guidance is more straightforward than the mechanistic detail might suggest. The pattern that consistently emerges from the research is one that reduces rapid blood sugar spikes, lowers overall insulin load, supports a favourable fatty acid ratio, and avoids the specific dairy components that drive IGF-1 and insulin signalling. This means prioritising whole grains over refined ones, choosing complex carbohydrates over simple ones, keeping sugary drinks and confectionery genuinely infrequent rather than treating them as everyday foods, and being honest about how much liquid milk and whey protein you are consuming if your acne is persistent. It means eating more fish, more vegetables, and more foods with a naturally low glycaemic index. It does not mean eliminating all dairy or never eating carbohydrates. It means understanding that some foods are consistently associated with more severe acne through well-understood mechanisms, and making choices with that understanding rather than without it.
One thing the research is clear about is that dietary changes alone are unlikely to resolve moderate to severe acne the way appropriate medical treatment can. Diet can meaningfully reduce lesion counts and improve outcomes, and there is even evidence that a low glycemic load diet is a predictive marker of better response to isotretinoin treatment in some patients. But diet works best as a complement to treatment rather than a replacement for it.
The Bottom Line
Diet does influence acne, and the evidence behind that statement is now substantial enough that dismissing it is no longer a defensible position. High glycemic load foods drive insulin and IGF-1 in ways that directly accelerate all four processes involved in acne development. Milk and whey protein contribute to the same hormonal environment through their insulinotropic and IGF-1-stimulating effects. Omega-3 fatty acids push back against inflammation and reduce IGF-1 in ways that consistently reduce lesion counts in controlled trials. But the degree to which any of this matters for your skin specifically depends on your individual biology, and the only way to know where your sensitivity lies is to actually test it. Use the research to identify what is worth eliminating first. Give it enough time to produce a real signal. Reintroduce things one at a time and pay attention. The research gives you the map. Your own skin over time gives you the territory. Both are necessary, and neither is enough on its own.
Reference
https://pmc.ncbi.nlm.nih.gov/articles/PMC11288498/
https://pubmed.ncbi.nlm.nih.gov/38982829/
https://pmc.ncbi.nlm.nih.gov/articles/PMC8971946/
https://pubmed.ncbi.nlm.nih.gov/20107753/
https://pubmed.ncbi.nlm.nih.gov/15692464/
