Editor's note: Felix Gussone is an intern with the CNN Medical Unit. He recently graduated from medical school in Munich, Germany. Do you have a weight-loss success story to share? Tell us how you did it and you could be featured in our weekly weight-loss story.
(CNN) -- Doctors frequently tell patients that they have to lose weight. But the majority of them don't know how it feels to be overweight or what it really takes to lose weight.
I do. Between my 17th and 19th birthday, I went from overweight teenager to lean adult by losing 99 pounds.
I was a happy teenager from a loving family. Food never served as a substitute for happiness in my life, and I had no reason for comfort eating. My mother didn't like fast food and always cooked healthy meals.
Knowing that, it seems absurd that I weighed 264 pounds at 16.
The reason for my weight gain was simple: I loved food (I still do!), I ate way too much, and I hated exercise.
Well, that's not totally true. My friends and I were passionate soccer players -- sometimes I would even start sweating when my Xbox game got too exciting.
"If I don't eat greasy fast-food, stay away from sweet soft drinks and avoid candies, I won't get fat," I used to think. So while my brother was having two potatoes, I ate four. He would have enjoyed a glass of milk in the morning if I hadn't already emptied the whole liter. He loved bread with some bacon; I preferred a lot of bacon with some bread.
If you eat more calories than your body needs you will gain weight. It's as simple as that. We are constantly told to focus on what we're eating, and yet we forget to think about how much we are eating.
Of course, I got bullied for being overweight. When you're fat, you're a target. I struggled with the teasing in the beginning but got used to it very quickly. That was dangerous -- getting used to people picking on your size means you're accustomed to being that size so there is no need for change.
I would still be extremely obese right now if it wasn't for a school trip to Paris in 2005.
I like French food and had a lot of it. But on the trip I got food poisoning and lost 7 pounds. Those 7 pounds were the spark that started the fire.
I realized that sometimes you have to RSVP yes when life sends you an invitation for change.
At first I thought: "Cool, I lost 7 pounds. I will try not to regain that weight."
Then I remembered there was something called exercise, and that experts said it could help you lose weight.
So I started using my mother's elliptical machine. I worked out for 15 to 20 minutes every single day. I also tried to eat half of what I had eaten before. Instead of four potatoes I ate two; instead of drinking a whole bottle of milk, I would only drink half of it.
My body responded well: Within two years I had lost 99 pounds.
(If I had known I would eventually be writing a weight loss story for CNN, I would have gone for 100).
I realized that if you and your body are hungry for change, weight loss can be fun, instead of a burden.
Luckily, I've never encountered the dreaded yo-yo effect. I have maintained my slimmer figure for seven years now. I never stopped exercising. After you've come so far, you don't want to take a risk and regain the weight because of laziness. I purposefully gained 22 pounds working out in the gym because I wanted to build muscle. Now my 6-foot 4-inch frame weighs 187 pounds. My body mass index is 22.
There are countless books on how to lose weight. All the authors seem to have priceless pieces of advice they've skillfully converted into cash. But in the end, I believe losing weight is a simple trade:
You feed your body the right amount of food and exercise. In return, your body burns fat. Even your wallet gets a little lighter because you have to buy new clothes.
After seven years of medical education, I have learned a lot about the health dangers of being overweight. I'm glad I took life's invitation to change as a teen. As a doctor who has been where they are, I hope to help others who are struggling with their weight do the same.