Summarize this article:

Being overweight can increase your chances of a gallstone, but losing weight too quickly can also cause gallstones. Aim to lose about 1–2 pounds (0.45–0.91 kg) a week.   Check your BMI to see if you're at a healthy weight for your height. If you're muscular, you may want to find out your body fat percentage instead. See your doctor for more information. Do not skip meals or fast when you are trying to lose weight. This can increase your risk of gallstones. You can break this down into 30-60 minutes of exercise a day. Aim to do moderate to vigorous cardio, like running, kickboxing, swimming, or riding a bike. Aerobic exercise like cardio can decrease your risk of developing a gallstone by helping you lose weight and improving your general health. A little bit of alcohol consumption each week may be able to help protect against gallstones. You might have a glass of wine with dinner or drink a beer on a night out. Stick to 1 drink every 1 to 2 days.  Moderate use means that you have no more than 1 drink a day on average. While it is OK to drink more on a special occasion, avoid drinking more than this on a daily basis.  Talk to your doctor about your alcohol consumption. The risks of drinking alcohol may outweigh the benefits.

Summary:
Lose weight slowly if you need to reach a healthy weight. Exercise for 5 hours a week. Drink a moderate level of alcohol.