It's often that one picture that will turn it around for you, one picture that comes out with the realisation that that is actually what you look like and it's going to be some hard work for you to fit back into your 'skinny' jeans.
That's exactly what happened to mum-of-two Sarah Hart. She was 21 stone when she was pictured next to her size 8 sister on their joint wedding day.
Sarah wore a 24 size bridal gown and dwarfed her petite sibling Amanda, who weighed just 8st 7lbs.
Sarah, of Caerphilly, south Wales, says: "My dress was absolutely huge. I needed to have it custom made.
"I was stuck in a size 24, while my sister effortlessly slipped into a stunning little dress."
After the wedding day, travel agent Sarah continued to pile of the pounds until she got so big she was unable to stretch an aircraft seabely around her waist on a holiday flight.
But instead of going on a traditional diet, Sarah had a gastric mind band therapy where she was hypnotised into believing she had a stomach the size of a golf ball.
She started eating tiny portions and shed over 11st in just under two years and now tips the scales at 9st 12lbs.
"My size was always in the back of my mind, but I was in denial at the time, because I was in love and happy," explains Sarah.
"Looking back at the photos, I'm shocked. I never realised I was that big. The weight just crept on me.
"I used photos like my wedding snaps as motivation tool I stuck them to my fridge to scare me away from snacking."
Sarah began piling on weight in her early years due to an unhealthy diet and an asth,a issue which required steroids. By the time she was 14 she weighed an astonishing 14 stone.
But, despite regular fat jibes from cruel classmates, Sarah put on a brave face and got by parading her 'bubbly' personality.
On the say she married her sweetheart Lee, an aircraft sprayer, in Cyprus in September 2000 - despite being just 19 years old - she was a size 24 and weighed 19 stone.
Ironically, she enjoyed a double wedding with her sister Amanda, now 35, who was a size eight.
After her wedding she began spending evenings sitting on the sofa enjoying calorific dishes such as chicken tikka masala with two naan breads, and two onion bhajis. She also regularly tucked into large portions of lasagne and spaghetti bolognaise.
Lunch for Sarah usually consisted of king size Mars Bars, while she also scoffed any other tasty snacks she could lay her hands on.
Sarah ballooned again after giving birth to her two sons Marshall, now three, and Harrison, five, reaching an incredible 21stone and 1lb.
The final straw came during the 2009 Christmas flight home from the house in France where they were living at the time.As she settled into her seat for the short hop back to Cardiff, she was unable to pull the seatbelt around her huge girth. The incident brought memories of her wedding day flooding back.
"Now I'm quite disgusted by how big I was. I would have done something much sooner if I had realised," she says. "Even my husband was shocked when we looked back at the wedding album."
Within weeks of the aircraft incident she spotted an article about the Elite Clinic in Marbella, Spain, which specialises in gastric mind band therapy.
The #800 hypnotherapy sessions, which took place in March 2010, were held in a relaxing environment while Sarah was hypnotised by Martin and Marion Shirran as she lay back in a comfortable chair.
Using a combination of hypnosis and Cognitive Behaviour Therapy, she was taken on a 'virtual tour' through the gastric band operation. Therapist Marion also used in-depth guided imagery and visualisation to fit an imaginary gastric band around the stomach, forming a pouch the size of a golf ball. During the procedure computer-driven equipment pumped a range of aromas into the room including those of a hospital ward, operating theatre and even the recovery room.
Within weeks of the hypnotherapy Sarah had lost a stone and by the end of 2010 she had lost seven stones.
Sarah - who is now so fit she recently ran a half marathon - adds: ''I feel so much much better now. If i want chocolate, I eat chocolate, but just not five bars of it. And I can't eat too much because I feel full, so I eat smaller portions.
''Now I will have cereal or porridge for breakfast, a light lunch and then a bit of meat and salad for tea.
''When I was fat things were difficult for me. I couldn't even do the housework without feeling exhausted.I even fell out with my sister for two months because she told me I was too fat. But they say the truth hurts.
"I would love to head back to Cyprus with Lee to renew our vows. Now I'm a 10 size and completely happy with my figure. If I did renew my vows, maybe I could wear Amanda's old dress, because it would finally fit."
Clinic owner Martin Shirran says: "Sarah is so typical of the clients that fly over for the treatment, she had tried all the traditional approaches to weight loss with little if any permanent results, her problem like so many others was down to her psychological relationship with food, once this was overcome, the results followed."