Obesity is a systemic disease characterized by chronic low-grade inflammation (Table 1).1–3 Also, obesity is one of the most prevalent non-communicable diseases worldwide. In the United States, it has doubled over the past decades, reaching a prevalence of 40% in adults, and an estimated 50% by 2030.4 In Spain, the current prevalence of obesity in adults is nearly 17%. Obesity is associated with an increase in inflammatory markers, such as tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP), and multiple cytokines, such as interleukins (IL) 6 and 18. Adipose tissue releases numerous proinflammatory mediators such as adiponectin, leptin, angiotensin II, resistin, visfatin, and IL-6.5 Obesity can also be considered an immunological disorder, as it is associated with a reduced immune capacity, and changes to the function of neutrophils, monocytes, lymphocytes, and macrophages.5 Additionally, it is associated with certain tumors (such as endometrial or colorectal cancer), cardiovascular disease, and changes to the microbiota.2,3 Given the complex pathophysiology of obesity and its association with an increase in proinflammatory mediators, hormones, and immune changes, it is not surprising that nearly 50% of obese patients present skin disorders.6

In recent years, a set of diets aimed at weight loss, improved physical capabilities, and management of various chronic diseases, whether cardiovascular, neurological, or dermatological, have proliferated. Among these diets, the ketogenic diet and intermittent fasting have shown very promising results in both traditional and sports medicine.7,8 Additionally, the Mediterranean diet has been established as a healthy eating pattern with a significant positive impact on health.9 Other popular diets include the “paleo” diet, the vegan diet, and the gluten-free diet (Table 2).

Below we will be reviewing the impact of these popular diets on the skin and dermatological conditions.

This was a narrative review of the scientific medical literature currenty available. From May through June 2023, were conducted searches on Medline and Google Scholar using the keyterms “diets,” “nutrition,” “skin,” “dermatoses,” “paleo,” “fasting,” “intermittent fasting,” “ketosis,” “ketogenic,” “gluten,” “vegan diet,” “psoriasis,” “acne,” “atopic dermatitis,” and “hidradenitis suppurativa.” This search was conducted in both Spanish and English. Articles were screened based on their abstracts and selected based on their relevance after a thorough review of the studies. Two authors (MMP, and JPC) conducted the search, article selection, and initial manuscript drafting. A third author (DMC) completed the search, and the manuscript drafting.

The ketogenic diet involves the restriction of carbohydrate-rich foods (at least, 30g/day to 50g/day) such as cereals, ultraprocessed foods, and sugar, in favor of a diet based on proteins and healthy fats, such as monounsaturated fats (nuts, avocado, and olives), and polyunsaturated fats (fish). There are multiple variations of this diet, including the Atkins diet, the modified Atkins diet (60% fats, 30% proteins, and 10% carbohydrates), and the low-glycemic index diet, among many others.7 The goal of the diet is to induce ketosis to obtain the required energy from stored body fat.

Intermittent fasting involves the voluntary abstention from food, or liquids for some time. It should be differentiated from starvation, which results in a lack of essential nutrients and severe complications. There are numerous wasy of fasting, being the most common of all 12-hour fasting, 16-hour fasting (with an 8-hour eating window), 23-hour fasting (with a 1-hour eating window), 24-24 (24-hour fasting followed by 24hours of regular eating), 36-12 hour fasting (36hours of fasting followed by 12hours of regular eating), and 5:2 fasting (2 days of fasting followed by 5 days of regular eating), among many others.7,10 Intermittent fasting> 12hours induces fatty acid metabolism and ketone production.10

Adverse events and contraindications of the ketogenic diet and intermittent fasting

Adverse events of these diets include dehydration, lethargy, hypoglycemia, acidosis, hydroelectrolyte and GI disorders.8 In recent years, numerous cases of prurigo pigmentosa associated with ketogenic diets have been described, popularly referred to as “keto rash.” It is characterized by pruritic and erythematous papules, plaques, or vesicles typically located on the trunk or neck evolving into retiform hyperpigmented plaques (Fig. 1). The appearance is characteristic, but the diagnosis can be challenging in the early stages of the disease (Fig. 2). The clinical picture often develops in just 1 month (ranging from 6 days to 4 months) after starting a strict ketogenic diet. The most widely recommended treatment is tetracyclines. Post-inflammatory hyperpigmentation is a complication in most patients.11

Figure 1.

Prurigo pigmentosa, keto rash. Multiple coalescing erythematous papules of reticular appearance located on the back. Hyperpigmented reticular plaques can be seen on the lower back region. The patient suffered from an eating disorder and was undergoing treatment for depression. Complete resolution of pruritus and erythematous plaques was seen after a 1-month course of doxycycline 100mg/day.

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Figure 2.

Prurigo pigmentosa, keto rash. Highly pruritic erythematous plaques on the dorsal back region. Note the subtle reticulated post-inflammatory hyperpigmentation on the central dorsal back region. The patient had been following a strict ketogenic diet for 4 months, resulting in significant weight loss. The clinical condition completely resolved after a 1-month course of doxycycline 100mg/day, along with diet discontinuation.

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Absolute contraindications for the ketogenic diet include porphyrias and pyruvate carboxylase deficiency, a rare neurometabolic disorder characterized by developmental delay, metabolic acidosis, and recurrent seizures in infancy.8 Some relative contraindications include certain mitochondrial cytopathies or carnitine deficiency.8 It is ill-advised for pregnant or breastfeeding women, young children, or patients with low weight, sepsis, liver or pancreatic failure, or severe lipid metabolism disorders.7

Mediterranean diet is characterized by the consumption of polyphenols from healthy foods such as fruits and vegetables, legumes, olive oil, grains, seeds, and fish, with a reduced amount of animal fats. Polyphenols have potent anti-inflammatory and antioxidant effects. Adherence to the Mediterranean diet has been shown to reduce cardiovascular events in long-term prospective trials,9 and be a valuable adjunct in the management of multiple chronic inflammatory diseases.31 Additionally, recent cross-sectional studies have associated it with greater well-being,32 and lower levels of depression and anxiety.30.

Gluten is a protein found in wheat, barley, and rye. Gluten sensitivity induces an abnormal immune response in certain individuals, triggering celiac disease, and causing intestinal atrophy and the disruption of nutrient absorption. At the skin level, it can lead to dermatitis herpetiformis.59 The overall prevalence of celiac disease is nearly 1%.60

In recent years, following gluten-free diets has become popular in the management of various chronic diseases. In most cases, the evidence is limited and controversial. In a recent single-center cross-sectional study of patients with psoriasis (n=1621), 5% had started a gluten-free diet on their own to control psoriasis.61 Similar results were seen in a study of 1571 patients with acne.62 A recent literature narrative review (of 49 studies and over 1000 patients) suggests that there is an association between gluten sensitivity and various dermatoses, such as psoriasis, palmoplantar pustulosis, and aphthous stomatitis, and these conditions could potentially benefit from gluten-free diets in patients with demonstrated gluten sensitivity. However, these authors do not recommend systematic screening for gluten sensitivity in these individuals. Still, systematic screening could be considered in selected cases refractory to conventional treatments. In the same review, other dermatoses that could benefit from an association with gluten are also suggested, including dermatomyositis, alopecia areata, urticaria, IgA linear bullous dermatosis, lupus erythematosus, or vitiligo.59 Regarding vitiligo, both diseases are primarily mediated by T cells and IL-2, IL-6, IL-17, and IL-21.60 In a single-center prospective study of 174 patients with vitiligo, 5 of them (2.8%) were diagnosed with celiac disease, a higher prevalence compared to that of the overall population.63

In relation to psoriasis, a single-center prospective trial from 2000 demonstrated an improvement in psoriasis-related lesions in patients with celiac disease and positive antigliadin antibodies at the 3-month follow-up.64 These results have been supported by a recent meta-analysis (of 18 studies and over 1000 patients) that showed a positive association between celiac disease and psoriasis, which would be explained by a common inflammatory link.65

The vegan diet is a strict vegetarian diet which avoids the consumption of meat, animal-derived foods such as dairy products, eggs, honey, and gelatin. Strict vegan diets can lead to various nutritional deficiencies, including iron and B-complex vitamin deficiencies.66 Multiple cases of pellagra have been described in these individuals as well.67 It is advisable for vegans to consider supplementing with B-complex vitamins.68 Multiple studies have associated this diet with depressive disorders too. Two recent systematic reviews showed different results: the first found a higher risk of depression and anxiety associated with this diet,69 while the second did not demonstrate that there was a clear association between depression and the vegan diet.70

Despite the scarce evidence available and controversy surrounding this diet, a balanced intake of vegetables and legumes is proposed as a useful tool in managing various dermatoses such as acne, psoriasis, and atopic dermatitis.68 A national survey of over 1000 patients reported overall fewer skin lesions and lower severity in patients with psoriasis treated with vegan diets compared to those who were not on such diets.71 However, a single-center prospective study (n=60) described more adverse events and delayed healing in vegan patients treated with photodynamic therapy for the management of actinic keratosis vs omnivorous individuals.72 Similarly, wound healing after surgical excision of skin tumors could be worse in vegan patients, with higher rates of dehiscence being reported, more frequent atrophic scars, and a worse overall scar appearance. This was demonstrated in a prospective trial (n=42) that compared vegan and non-vegan patients 6 months after surgery.66 As for the response to fractional radiofrequency as an anti-aging treatment, a comparative prospective trial (n=60) found that vegans had poorer mid and long-term responses compared to omnivores.73 Additionally, it has been reported that vegan patients may have a high consumption of furocoumarins and a more adverse events with UVB phototherapy compared to vegetarians or omnivores, suggesting that phototherapy protocols should be adapted in these cases.74

Despite the therapeutic revolution represented by biologic drugs and targeted molecules in Dermatology, it is essential to address modifiable factors such as diet, and dermatologists can play a crucial role in recommending interventions in this regard. In our routine clinical practice, it is not unusual to encounter patients who follow popular diets such as the ketogenic one, intermittent fasting, vegan diet, gluten-free diet, or the “paleo” diet, or who want to know more about the benefits of these dietary regimens in the management of their dermatological diseases. The Mediterranean diet, the ketogenic diet, and intermittent fasting have the highest level of evidence to date in the management of chronic inflammatory diseases, including cardiovascular, metabolic, neurodegenerative diseases, and inflammatory dermatoses. The ketogenic diet and intermittent fasting have been associated with reduced cutaneous and articular activity in psoriasis, and better disease control in hidradenitis suppurativa, or in other entities such as acne, or atopic dermatitis. The Mediterranean diet has also been associated with better disease progresion in patients with psoriasis, hidradenitis suppurativa, acne, atopic eczema, chronic spontaneous urticaria, alopecia, and even skin cancer. Additionally, the Mediterranean diet is one of the most sustainable diets ecologically speaking.75 However, most studies conducted with these diets in Dermatology are retrospective, or case-control studies, or exhibit obvious methodological biases that hinder the generalization of these findings.

Regarding the gluten-free diet, although there might be an association between gluten sensitivity and certain dermatoses, empirically speaking, it should not be prescribed, or recommended for overall gluten sensitivity screenings.59 Similarly, very restrictive diets such as the vegan one can delay wound healing, and induce a series of adverse events after dermatological procedures.72–74

This article is limited in that it is a narrative, non-systematic review of the medical literature currently available. Additionally, many of the studies included have low methodological quality, with many having small sample sizes, no clear definition of inclusion criteria, and being retrospective in nature. Both these factors make it difficult to generalize the findings and conclusions reported.

Multiple diets have gained popularity in recent years. The Mediterranean diet, the ketogenic diet, and intermittent fasting could be an additional therapeutic tool in the management of various chronic inflammatory dermatoses, or even play a role in reducing the incidence of malignant skin tumors. However, more studies are needed to corroborate these results and make recommendations with a higher level of evidence, and determine which diet is superior in the management of these diseases.

None declared.