The typical day sees the average man say or think three negative things about themselves – a total of 1,095 a year – while women do so four times a day, or 1,460 times annually.
Other areas people put themselves down about included their teeth, stomach, and legs.
The research, commissioned by Tu Clothing, also found one in four (26 percent) have become more negative about their appearance as they’ve got older.
It emerged that when deciding what to wear, adults contemplate an average of five outfits before committing – with feeling too fat or old, and not liking arms or legs being on display, among the top reasons for feeling uncomfortable.
As a result, those polled like to play it safe, with black being the most confidence-inducing colour to wear.
This was followed by blue and grey – while only 19 percent feel comfortable in orange, and 21 percent are happy wearing yellow.
But 21 percent wish they could channel their childhood freedom to chuck on what feels good.
Actress and TV presenter Zoe Hardman, who is working with Tu to encourage people to “dress for joy”, said: “With summer now upon us, many of us fear getting body parts out that are hidden the rest of the year – including stomachs, thighs, and upper arms.
“This summer, I want everyone to tap into their inner child and adopt a carefree attitude when it comes to getting dressed.
“Kids love to wear what makes them feel great, and don’t give a second thought to other people’s opinions.
“I want to help encourage the nation to embrace their own unique style, care less about what others think, and have fun putting outfits together.
“Summer is a great time to embrace bold colours and patterns, which increase both positivity and confidence.”
The study also found women feel least confident in bikinis (31 percent) and swimming costumes (33 percent), while men lack self-esteem in swimming trunks (20 percent) and tight fitted t-shirts (19 percent).
Almost a quarter of adults (23 percent) generally struggle to find clothes they feel comfortable in.
And the same number (23 percent) admitted they care too much about what others think of them, while 18 percent fear summer because they don’t know what to wear.
Meanwhile, 28 percent worry they are too old for certain styles – a feeling which began aged 32 for women, and aged 38 for men.
A fifth have even been told by others that they are “too old” for certain items – with the poll revealing adults think 44 years old is the maximum age to wear a bikini.
Anything above the age of 47 was considered “too old” to wear leggings, age 43 for crop tops, and 46 for wearing mini-skirts.
Of those polled who are parents, three in ten (31 percent) have let their little one select an outfit for them from their wardrobe, while 27 percent have done so when shopping.
More than a quarter (27 percent) have even worn matching outfits with their offspring.
And a third (34 percent) of mums and dads polled, via OnePoll, said their child doesn’t care what people think about what they’re wearing.
Emma Benjafield, director of product at Tu Clothing, said: “I’ve been really looking forward to making the most of this summer, and there’s no better time to embrace your body and wear colours, prints, and patterns.
“We want to encourage people of all ages to simply have fun with dressing up, to not be afraid to wear what they want, nor to worry what others think.
“The results show people think they’re “too old” for certain clothing items, but we want to change this myth.
“Everyone should wear what they want, how they want, and when they want. Fashion, after all, should be fun and make you feel good.”