In the early 2000s, he’d worked for Handspring, a manufacturer of PDAs, or personal digital assistants, that went on to merge with Palm in 2003. “Write down everything that you eat in a notebook.” “You need to start counting your calories,” the trainer advised, tapping the book. It contained calorie counts for about 3,000 foods. At the end of the first session, after Mike Lee and his fiancée had sweated off maybe half a pound, the trainer handed them a small book. His fiancée also wanted to lose some weight before the big day, so the couple went to see a personal fitness trainer at their local gym, 24 Hour Fitness. The only trouble was he had put on weight over the summer and didn’t want to walk down the aisle with a pudgy tummy.

It was the summer of 2003 and Mike Lee, a 32-year-old Silicon Valley marketing executive, was looking forward to his wedding day later that year. Trackers is now available on Kindle and in other digital bookstores.

In this exclusive excerpt from ReadWrite founder Richard MacManus’s new book, Trackers: How Technology Is Helping Us Monitor & Improve Our Health, he reveals founder Mike Lee’s secrets for building an app that has helped millions lose weight. MyFitnessPal recently sold to Under Armour for $475 million.

Myfitnesspal diet