Obesity has become more common in people with type 1 diabetes for the very same reason it has become more common in all people. Weight gain causes insulin resistance and an increased need for insulin. Weight gain makes it harder to control blood sugar. This may also result in a metabolic syndrome involving lipid metabolism disorders and high blood pressure.
Therefore, for a person using insulin therapy, weight gain may also be down to insulin doses that are too big. If the amount of insulin is too large, it may lead to increased appetite and blood sugar dropping too low between meals, during exercise and at night. A fear of hypoglycaemia is also a common reason for overeating.
If you are overweight, it's advisable to prevent excessively low blood sugar levels by anticipating and, if necessary, reducing insulin doses. It's good to discuss possible fears related to low blood sugar levels with your doctor or nurse, and if necessary, talk about the issue with a mental health professional
Adjusting insulin doses
If you use insulin and want to lose weight, you simultaneously need to reduce both the amount of insulin and the carbohydrates consumed. As the weight decreases and also with increased exercise, insulin sensitivity typically improves. In this case, the relative need for basal insulin and possibly also mealtime insulin decreases. If you aren't already using a glucose sensor, it would be advisable to discuss its adoption with your doctor and nurse. With the help of a glucose sensor, it's easier to adjust insulin doses to different amounts of food and exercise.