In the last few decades we have seen a dramatic rise in the levels of obesity in both adults and children – tripling since 1975 (WHO data). It is defined as a person having a body mass index (BMI) of 30 kg/m-2 or greater, (above 25 kg/m-2 is considered overweight). The increase has had major implications for healthcare and healthcare planning as obesity is associated with a range of comorbidities such as hypertension, hyperlipidaemia, certain types of cancer and diabetes. The skin as an organ can also be affected by the condition. In this blog, I will be looking at the obesity and skin – reviewing papers which have investigated this issue.
In adults, white fat cells, known as adipocytes, perform two main functions - as an energy store but also as a form of insulation for the body. Weight gain leads to an increase in the total number of adipocytes in the body. Fat cells are able to produce leptin (a hormone controlling appetite) and a range of chemical mediators and other hormones including sex hormones. Hence, why being under or over-weight can lead to fertility problems. In addition, macrophages located within the adipose tissue can produce TNF-α, interleukin-1 (IL-1) and interleukin-6 (IL-6) and other pro-inflammatory cytokines which can lead to insulin resistance and the development of diabetes.
Obesity and the skin
The first thing to note is that despite the fact that obesity has been increasing, there is little research which has focussed specifically on the effects on the skin. Obesity is strongly associated with diabetes and consequently this may magnify problems for the lower limb and foot such as increased risk of infections, ischaemia and delayed wound healing which have all been well documented in research. Moreover, the dermatological manifestations of diabetes have been discussed (1-3).
In 1999, Garcia-Hildago et al. (4) undertook a survey of 156 patients defined as obese (of which 76 were known to have diabetes). Their BMI ranged from 27 - 51 kg/m-2 and no control group was used. The most common dermatological conditions were plantar hyperkeratosis (more on that later), a skin condition called acanthosis nigricans and skin tags. The statistical analysis showed that increasing levels of obesity showed increased prevalence of skin disease. Acanthosis nigricans is a skin disease characterised by hyperpigmentation and skin tags in the body folds such as groin, axillae and neck. The skin takes on a velvety texture with numerous skin tags developing within the lesions. The condition in most cases is associated with obesity and insulin resistance, but in a few cases can occur as a dermatological manifestation of internal malignancy (5).
Acanthosis Nigricans (CC Licence)
Guida and colleagues (6) followed this up 11 years later and undertook a study comparing the skin of 60 obese patients with 20 non-obese individuals – none of the subjects were diagnosed as having diabetes. They further sub-divided the obese patients into three categories of obesity. They concluded, once again, that plantar hyperkeratosis was highly prevalent amongst the most obese patients with additional strong correlations with skin tags and acanthosis nigricans. In addition, they noted intertrigo as another skin problem. Intertrigo is a skin condition where rubbing of adjacent skin folds leads to irritation, maceration and accumulation of sweat which can subsequent lead to bacterial, fungal or mixed superficial infections. As condition precipitated where body folds overlap a sharp margin is observed on the lesion corresponding to the body fold. The interdigital areas between the toes can be affected with this condition. In addition, the researchers in this study compared trans-epidermal water loss (TEWL) between the groups and discovered that obesity increases TEWL and dry skin in these patients prevails.
A further study in 2018 (7) reported dermatoses in 600 adults (450 obese and 150 non-obese). Thirty percent of obese patients also had diabetes. Again, it was confirmed that plantar hyperkeratosis, skin tags and acanthosis nigricans were all associated with obesity. In addition, venous insufficiency was also reported.
Plantar Hyperkeratosis and Obesity
It is interesting to note that plantar hyperkeratosis was a consistent feature of obesity in all these surveys. In podiatry, this is often observed but not something that is particularly reported in podiatric literature. Studies have shown that obese patients exhibit higher plantar pressures when standing and walking, but also have an increased forefoot width (8). Studies in children has also shown that overweight children have flatter feet with a greater weight bearing surface than their non-obese counterparts (9) and greater foot dimensions (10). The typical hyperkeratosis in adults with obesity has been described as a hyperkeratotic area around the rim of the heel with corresponding callus under the medial edge of the first metatarsophalangeal joint (11).
Sensitivity and the skin
Research on the forearm skin has demonstrated that patients with obesity are less sensitive to pinprick (12). This is believed to be a dampening effect due to the increased subcutaneous adipose tissue. This phenomenon is an interesting one – of course, it is well known that obese patients are more likely to suffer pressure sores, which could be in part due to dampened sensation. Whether there is a similar effect on the foot remains unresearched.
Skin infection
A number of studies have shown that patients with increased BMI are at an increased risk of infections such as bacterial and fungal skin infections (13). Cellulitis, a recurring topic on this blog site, has been shown to be associated with an increased BMI. As well as the increased risk of infection, it has been shown that increased BMI is a predictor for a poor response to treatment of skin and soft tissue infections (14). One study of 500 overweight and obese patients in Turkey found increasing levels of onychomycosis in these groups (15). Interestingly, in a study of a topical nail treatment it was also shown that patients who were obese were less likely to respond as well than patients with a normal BMI (16).
Webspace Intertrigo (CC licence)
Summary
From the limited skin surveys available, it appears that obesity can lead to increased plantar callus, particularly around the heels and dry skin. In addition, skin infections such as intertrigo and fungal foot infection may be more prevalent. Work has suggested that infections in patients who are obese are likely to be more difficult to eradicate than those in patients with a normal BMI.
References
1. Bristow I. Non-ulcerative skin pathologies of the diabetic foot. Diabetes Metab Res Rev. 2008;24 Suppl 1:S84-9.
2. de Macedo GM, Nunes S, Barreto T. Skin disorders in diabetes mellitus: an epidemiology and physiopathology review. Diabetol Metab Syndr. 2016;8(1):63.
3. Makrantonaki E, Jiang D, Hossini AM, Nikolakis G, Wlaschek M, Scharffetter-Kochanek K, et al. Diabetes mellitus and the skin. Rev Endocr Metab Disord. 2016.
4. García-Hidalgo L, Orozco-Topete R, Gonzalez-Barranco J, Villa AR, Dalman JJ, Ortiz-Pedroza G. Dermatoses in 156 Obese Adults. 1999;7(3):299-302.
5. Griffiths CE, Barker J, Chalmers R, Bleiker T, Creamer D, editors. Rooks's Textbook of Dermatology. 9th ed. London: Wiley; 2016.
6. Guida B, Nino M, Perrino NR, Laccetti R, Trio R, Labella S, et al. The impact of obesity on skin disease and epidermal permeability barrier status. J Eur Acad Dermatol Venereol. 2010;24(2):191-5.
7. Ozlu E, Uzuncakmak TK, Takir M, Akdeniz N, Karadag AS. Comparison of cutaneous manifestations in diabetic and nondiabetic obese patients: A prospective, controlled study. Northern clinics of Istanbul. 2018;5(2):114-9.
8. Hills AP, Hennig EM, McDonald M, Bar-Or O. Plantar pressure differences between obese and non-obese adults: a biomechanical analysis. Int J Obes. 2001;25(11):1674-9.
9. Dowling AM, Steele JR, Baur LA. Does obesity influence foot structure and plantar pressure patterns in prepubescent children? Int J Obes. 2001;25(6):845-52.
10. Morrison SC, McCarthy D, Mahaffey R. Associations Between Obesity and Pediatric Foot Dimensions. 2018;108(5):383-9.
11. Hahler B. An overview of dermatological conditions commonly associated with the obese patient. Ostomy Wound Manage. 2006;52(6):34-6, 8, 40 passim.
12. Khimich S. Level of sensitivity of pain in patients with obesity. Acta Chir Hung. 1997;36(1-4):166-7.
13. Lewis SD, Peter GS, Gomez-Marin O, Bisno AL. Risk factors for recurrent lower extremity cellulitis in a U.S. Veterans Medical Center population. Am J Med Sci. 2006;332(6):304-7.
14. Cieri B, Conway EL, Sellick JA, Mergenhagen KA. Identification of risk factors for failure in patients with skin and soft tissue infections. Am J Emerg Med. 2019;37(1):48-52.
15. Doner N, Yasar S, Ekmekci T. Evaluation of obesity-associated dermatoses in obese and overweight individuals. Turkderm. 2011;45:146–51.
16. Elewski BE, Tosti A. Risk Factors and Comorbidities for Onychomycosis: Implications for Treatment with Topical Therapy. The Journal of clinical and aesthetic dermatology. 2015;8(11):38-42.