The fact that obesity prevents acne is one of the classic homegrown theories discovered by the acne-suffering population at large and not generated by dermatologists and all their studies. Countless teenagers have noticed the relationship after observing their classmates, just like stress and chocolate supposedly causing acne.
People’s theories are often crazy-sounding yet strangely logical. Some have theorised that fatter people are fatter in the first place because they’re relaxed, less stressed about life. Others insist that fat people’s genetics are engineered towards storing fat on their stomachs and away from pumping out pore-clogging oil on their face.
A particularly popular theory is that the faster metabolisms of thin people are constantly forcing acne-causing toxins through their skin. Supposedly, obese people’s toxins accumulate harmlessly in their fat cells instead, causing their skin’s toxin channels to literally collapse like a disused mine cart tunnel.
Here, our strong viewpoint is that fatness suppresses acne-causing hormones like DHT and testosterone and increases hormones behind smooth baby-faces like estrogen. Both of these hormonal connections to acne are confirmed, but there’s a catch.
As of 2019, the studies directly analysing BMI and acne, and for some reason they’re piling up exponentially while raw honey and magnesium are ignored, are still extremely conflicting.
2019 study says obesity causes acne…
As recently as March 2019, a study laid waste to the observations of millions of teenagers. Bespectacled, white-haired scientists broke into schools across Southwest Poland (or maybe politely knocked on the front door) and gathered 143 students, 85 boys and 48 girls, aged between 12 and 18.
Their parents completed a dietary questionnaire, while their BMI was professionally measured. Their acne was assessed on a scale of 0-3, graded as not present, mild, moderate or severe. The terrible trio were all analysed: comedogenic acne (whiteheads), papulo-pustular acne (red and angry) and nodulo-cystic acne (annoyingly unpoppable cysts). Their face, shoulders and back were analysed separately.
When the conclusion came, it fanned the flames of the debate further. While the obese children were no more likely to have acne than the skinny ones, the acne they did have was much more severe. The relationship was identical in both 12-14 and 15-18 year olds.
Fatter children were particularly cursed with both cystic and red, angry papulo-pustular acne. High BMIs also correlated to extra back and shoulder acne.
Perhaps they were just “respecting tradition” and eating greasy Polish sausage all day? Not so – the diet composition differed little between the high BMI and low BMI groups.
For comedogenic acne, the whiteheads which are so fun to explode on the school toilet’s mirror, the average BMI was actually lower, but it didn’t sway the overall verdict. The results “clearly indicate an association between overweight/obesity and acne“. This flips the conventional wisdom on its head.
…but a superior study says it protects
Yet just two months earlier, a massively superior study disagreed. The good news for Greasy Burgers Inc. was that fatness protected against acne. The better news was that the sample size was 4000 times bigger.
The scientist found a ready made source of test subjects in the Israeli army, and among the 600,404 soldiers tested, being overweight or obese was “inversely associated with acne in a dose-dependent manner“. As soldiers moved up the scale from thin, to normal, overweight, or obese, their chances of acne gradually declined. For example, 18.7% of the male soldiers had acne overall, but this decreased from 19.9% in thin soldiers to 13.9% in severely obese ones. The women’s figures were 16.9% and 11.3%, with an average acne occurrence of 16.3%.
Naturally, as new recruits, they tended to be young, averaging at 18.9, making it a tidy comparison to our first study. The data was collected from 2002-2015, meaning that if the Israel cafeteria lost their mind for just two years and fed the soldiers gummy bear flavoured gruel, the study would override that.
The standout figure was that severely obese soldiers were 50% less likely to have acne than thin ones. With every one point decrease in BMI, using trusted World Health Organisation definitions, the chances of acne increased by 3.2%.
Study author Dr Igor Snast even speculated that increased aromatase activity by fat tissue would covert more testosterone into estrogen, the exact same theory I wrote about here. This study meshes completely with the acne hive mind’s observations.
Other studies say fatness is neutral
However, before you dash to the supermarket and buy a bottle of Farmer Heartburn’s prime pizza grease, you need to see four more recent studies, which only add more mist to this swamp of a debate:
Study one – from the deserts of Israel, we head to a university campus in southern Nigeria, and 105 students with an average age of 22. Their face was divided in to 4 sections, and comedones, papule, pustule and nodule were all counted.
The verdict: BMI alone had no correlation with acne whatsoever. When combined with physical exercise and age, there was a correlation, but this vanished using weight alone. The study was fairly strict, as patients undergoing antibiotic treatment, insulin resistance and even stress were excluded.
Study two – round two in Nigeria yielded very different results. This time, overweight Nigerians were more likely to have acne, but with no effect on the severity of that acne.
Considering the gigantic differences here, it’s amazing that other studies were so different. 81.7% with a BMI of 25+ had acne, compared to 61.1% for 18.5-24.99 and just 42.0% for less than 18.5. The sample size was dramatically larger, with 1079 nine to twenty year old students from four secondary schools in Ibadan city.
Study three – scientists crept around a Nepali hospital and harvested data on 249 acne patients. They were mostly aged 11-20, but the age range was particularly wide, at 10-44. The female/male ratio was 1/1.4, and patients taking medications were banished.
There was no significant relationship between the patients’ BMI and their acne counts. For example, 65.5% of the patients were normal weight, and 12% overweight, and this barely changed between the acne grades. Grade 2 (mild acne) actually had the highest mean BMI, at 21.4 versus 21.3 for grade 4 (severe acne).
Study four – the first ever meta-analysis of acne and obesity, a judgement on 4 different studies compiled together. Even scientists can’t resist investigating this age-old question, despite admitting that they’d never recommend getting fatter. Only the cream of the crop were included. Other studies were deemed too small, not focused on BMI, or fatally flawed.
When pooled, the studies had 983 acne patients and 1313 controls. Skin cancer had a connection to obesity, but acne? No meaningful correlation in any direction, not when pooled. The scientists admitted that their analysis was limited, because of only 4 studies making the cut, varying sample sizes, and constraint to English-speaking studies, but the studies they did include were all high quality.
Which studies are reliable?
As you might guessed, some of these studies’ credibility is hanging by a thread while others are a sturdy as a 16th century suit of armour.
There’s no getting around that the giant reliable study with 600,404 volunteers is the one where obesity is the most beneficial for acne. Our final tally since early 2018 is 1 beneficial, 1 definitively negative, 1 half negative and 3 definitively neutral.
Immediately though, three studies are hobbled by both their small sample size and more unique problems. The shocking “obesity causes acne” study boasted of identical diets between the different BMI groups, but the questionnaire was self-reporting, and they admitted that the patients could have lied in guilt.
What’s more, responses to the questionnaire were lower than they hoped for. Only sweets had a significant relationship with acne, but strangely, in all their sugary glory, they improved acne. This one result immediately rings the alarm bells.
Meanwhile, the neutral hospital study had only 2% of their patients as obese and 12% overweight. With only 249 participants to start with, this makes seeing a clear picture impossible. Furthermore, because every participant was an acne patient, the study could only possibly judge acne severity to start with.
Much easier to analyse was the neutral Nigerian study, with 28.6% overweight and 17.1% obese. They also counted the pimples by hand using brain surgeon precision, and had brutally strict exclusion criteria, but there’s no escaping the measly 105 participants, particularly when diet and lifestyle controls were missing.
The studies aren’t useless, like with only 20 participants, but the protective Israeli army study boasted thousands of times more patients, not to mention 14 years of data.
As fresh recruits, they also probably ate similar diets, and underwent similar physical training regimens. The 600,404 soldiers probably had inbuilt lifestyle controls, focusing the scientists like a laser on obesity’s consequences.
What of the half positive Nigerian study? It had the second biggest sample size (1079 schoolchildren), and gave a properly representative slice of one African city. Because they lived in similar schools and cultures, their diets probably coincided more, making body fat truly responsible. Even walking the same route to school and attending the same gym lessons make their physical activity more consistent.
With the neutral meta-analysis, the big failure was the restriction to four studies. This meta-analysis of milk, for example, included 13 studies (hint: it causes acne). However, the end result of 2296 participants was plentiful, and the scientists’ other self-confessed flaws like geographical variation and inconsistent patient exclusion criteria (like taking medications, etc) were mostly technical nitpicking around the edges.
We are left with one superbly conducted study in favour of obesity clearing acne, and one well-conducted study against and on the fence each. In short: the mystery is still unsolved.
Fat versus clear skin #1
Which leaves us back at square one. The evidence still points towards protection, but are there any legitimate reasons why fatness would cause acne?
According to the Polish scientists, the main antagonist was unmasked as the hormone IGF-1, a feared acne master molecule. IGF-1 pushes the buttons of dead skin cell turnover, oily skin, and testosterone’s acne-causing power.
There’s a fatal flaw though: this study and this study both found that body fat led to lower IGF-1 levels, not higher. Only this study showed the opposite, and how body fat would actually increases IGF-1 is a mystery.
With estrogen, we know the process well: individual fat cells churn out the aromatase enzyme which converts bloodstream testosterone to estrogen. Compared to IGF-1 it’s all written in stone.
Even then, we don’t know whether a trickle of IGF-1 would counteract the flood of estrogen anyway. The IGF-1 theory is uncertainty built upon a crumbling foundation of uncertainty.
Fat versus clear skin #2
The real reason why obesity might accelerate the pimple conveyor belt is actually low-grade, chronic inflammation. Scientists once believed that fat cells (adipocytes) were inactive blobs of energy storage, but it turns that they’re extremely active, pumping out acne-causing inflammatory chemicals like interleukin-6 and TNF-a like there’s no tomorrow.
Fat itself also releases the master molecule NF-KappaB, which stimulates pro-inflammatory genes further, creating a self-perpetuating, rapidly accelerating spiral of fire. This is actually caused by body fat itself and not the pizza paradise that comes with it. Fat cells even churn out false distress signals, protein complexes normally used by the immune system to target deadly viruses, stoking inflammation without provocation.
If there’s any reason why obesity causes acne, it’s inflammation. The question is over its power, whether genes can save the day, whether lifestyle can calm it.
The huge disturbances in DHT, testosterone and estrogen are most likely dominant, but certain circumstances could tip you into the abyss, like if you lacked important anti-inflammatory nutrients elsewhere.
Certain genetics could even suppress the aromatase enzyme, making your body fat only half as estrogenic. If fat can churn out pro-inflammatory chemicals, maybe it could also churn out a secret acne substance unknown to humanity, a dark overlord pulling the puppet strings of every acne process.
The verdict
That’s why this article has two conclusions. Firstly, it still looks obesity is an armour against acne, but secondly, there are undeniably dark clouds of mystery floating around.
The best designed study here found resolutely that obesity prevents acne. The margins weren’t miniscule, they were enormous, and the main “obesity causes acne” study was crippled. However, there’s easily enough conflicting studies to open the chasms of doubt.
Also, this article is about body fat itself. Never forget that in the real world, your skin depends strongly on the foods you use to get fat. If you’re a portly 16th century king living in a gloomy castle with bowl after bowl of fresh fruit stretching across a jewel encrusted dining table 20 meters long, you’ll be eating far more anti-inflammatory compounds.
If your beloved breakfast staple is McDonalds flavoured cornflakes, you’ll be eating cheap cooking fats instead. If you’re a gluttonous businessman lounging happily in the Mediterranean sun, your extra vitamin D will be suppressing inflammation.
While our main verdict hasn’t changed, the mystery of obesity and acne lives on.
Thanks for reading!