Weight and type 1 diabetes

How common it is

In one UK hospital clinic, 53% of adults with type 1 diabetes were overweight or living with obesity.

Why it happens

• Intensive insulin treatment, which protects against complications, is associated with weight gain; this was seen in the large DCCT trial
• Treating and preventing hypos means extra food, and fear of hypos can mean eating "just in case" and avoiding exercise
• The same things that affect everyone's weight: sleep, stress, work patterns and family habits

"Double diabetes"

Some people with type 1 diabetes also develop insulin resistance, the main feature of type 2. Insulin doses creep up and weight increases. In the same UK clinic, insulin resistance of this kind was far more common in those who were overweight.

Losing weight with type 1 diabetes

• Reduce insulin in step with reduced food intake, with your diabetes team's advice, so that eating less doesn't cause more hypos
• Fewer hypos means fewer extra calories. Settings and technology that reduce hypos often help weight
• Very low-carbohydrate and ketogenic diets, and long fasts, can be done, but they raise the risk of hypos and ketoacidosis and need planning and closer monitoring with your diabetes team
• Plan exercise: adjust insulin and carbohydrate beforehand, and use your CGM or closed-loop exercise mode
• Never stop basal (background) insulin
• Check blood ketones if you are unwell, or if you have cut your insulin and your glucose is high

Follow the sick-day rules your diabetes team gave you. If blood ketones are high, or you are vomiting and can't keep fluids down, get medical help straight away.

Why specialist input helps

Most weight programmes are written for people without diabetes or with type 2 diabetes, and their advice on calories or fasting doesn't account for insulin. Weight loss in type 1 diabetes works best as a joint plan for food, insulin, hypos and activity, and putting that plan together is a particular interest of mine.

Some people ask about weight-loss medicines. Whether any treatment is suitable in type 1 diabetes is a specialist decision made after assessment, and I discuss it at the consultation.