From a young age we’re taught not to judge a book by its cover, but staying true to this lesson is easier said than done.
As a result, he says, people with an attractive face get a head start in life: they earn more money and have happier personal lives than their uglier neighbours.
His words, which partly echo Charlotte Hakim's controversial notion of 'erotic capital' -- that men and women (but mainly the latter) should exploit their appearance and sex appeal for social gain -- may be unsettling, but Dr Mendelson's ideas are far from ill-informed.
His new book 'In Your Face' draws on various studies, together with personal and professional experience, to set the record straight about cosmetic surgery and talk frankly about why looks matter.
Dr Mendelson revisits the notion of 'pulchronomics', a term coined by US economist Daniel S Hamermesh in 2011 to identify the economics of beauty. Hemermesh estimates that the economic value of beauty totals approximately $230,000 over the course of a a lifetime.
Conversely, Dr Mendelson argues that the opposite can also be true.
"There has been a study on less attractive men and how much their looks cost them," he tells HuffPost UK Lifestyle. "Throughout their lives these men have to work harder and perform better than good looking men, but ultimately they are still getting less because they aren’t seen to be so nice."
But it's not just earning potential that increases with beauty, he says, people are also treated better.
"We associate people who are attractive as being good people," he tells HuffPost UK Lifestyle. "People who don’t look so nice are constantly being labelled and police target people who look like criminals."
To further his point he reaches for his iPhone.
"Look at this," he says, revealing a photograph of his dog, which (admittedly) is adorable.
"As a puppy, even people who didn’t like dogs would pick her up and pet her. Now she is the sweetest dog and always sees the good in other people because she has been treated well."
He adds:"A stray dog would never have that inner beauty."
But those wondering which facial components will bring fortune and happiness may be disappointed to learn that Dr Mendelson -- whose job it is to make people attractive -- is unable to pinpoint what constitutes beauty.
"Beauty is subjective," he tells HuffPost UK Lifestyle. "It's about the quality that pleases the senses and the response it invokes on the individual."
He dismisses attempts to define beauty with mathematical formulae, arguing that the brain is too sophisticated to be deciphered in such a way.
"Often there’s no one beauty," he explains. "Claudia Schiffer, who has very heavy eyes and high cheekbones, is striking, but she’s not what is generally considered a ‘true beauty’."
So if there is no concrete way to define beauty, why do Dr Mendelson's patients insist on having cosmetic surgery in the first place?
"People don’t have surgery to look better, they have surgery to improve the way they feel about the way they look," he explains.
Surgery is just a vehicle to improving self-esteem, he says, and it's important that patients understand that.
"During the consultation period you have to make sure that the surgery is going to lead to happiness and that the expectation of the patient is aligned with what you are going to do."
Many of his patients opt for "subtle" procedures and tend not to tell husbands, mothers or friends.
The majority of Dr Mendelson's patients chose to have rejuvenation surgery, to reduce the signs of ageing, or as he puts it "to remove the mask".
"Women’s faces are prone to ageing more than men because the tissues are finer," he says, which partly explains why so many of his patients are female.
Many patients come to him with a face they no longer recognise, he adds, after traumatic life events such as a divorce, losing a loved one or even illness, have taken their toll.
"It’s a lot of money to get self-confidence, but self-confidence is so important in our interactions with others and the world."