Watermelon is a very good choice, of what, to eat, while losing weight. It's low in calories and high in nutrition. It contains lycopene, which has been found to to lower your risk of cancer, heart disease, and age-related vision loss due to macular degeneration. One cup of cubed watermelon contains less than 50 calories and is pretty filling. So it is a good idea to incorporate a good amount of watermelon into your diet. I would not recommend eating only watermelon to lose weight, though. This could easily result in nutrition deficits and cause more harm than good. However if you eat watermelon, along with a balanced healthy diet, you will reap the benefits, including losing weight. I'm discovering a lot of losing weight is what you do eat more than  what you don't eat. If you enjoy your diet you are a lot more likely to stay on it. After all this really isn't a diet so much as a change in your way of eating. Losing weight is one thing that will just happen, if you need it to, along with improving your overall health.