Statistics have shown that most women gain weight during their 20s. Here's why... The research, published recently in Health magazine, claims that most females put on an average of 2.2lbs per year between the ages of 18 and 30 - that's a total of 26.4lbs! Experts claim that this common weight gain can be attributed to starting a career (less time for exercise and more time sitting at a desk), eating out and drinking regularly, and a more inactive lifestyle compared to teenage years. The diet and exercise regime starts on Monday, after we've spent the weekend sitting, eating and drinking, right?