There are several risk factors for developing diabetes. Many of these have to do with lifestyle. Obesity is clearly a risk factor. It therefore takes more insulin to keep the blood sugar under control. This is referred to as insulin resistance.
Sedentary lifestyle is another risk factor.
By not exercising, a person tends to lose muscle tissue and gain fat tissue. As above, this leads to insulin resistance. A high-carbohydrate diet is a risk factor, too. Carbohydrates are molecules that are short to long chains of sugar molecules. The body digests and converts these to glucose very quickly.