Last year I was included in a discussion on a Facebook group for athletes with diabetes about how hard it can be to lose weight through exercise. While I don't have all the answers on this topic, here are some ideas about what can make you gain weight or keep you from losing weight with diabetes, based on my decades of professional and personal experience with diabetes and weight management, and what you can do about it.
Insulin: My former graduate student with type 1 diabetes went on an insulin pump and promptly gained about 10 pounds, even though his blood glucose control improved only marginally. Why does it happen to so many insulin users? As an anabolic hormone, insulin promotes the uptake and storage of glucose, amino acids, and fat into insulin-sensitive cells around your body (mainly muscle and fat cells). It doesn’t matter whether it’s released naturally, injected, or pumped. Going on insulin therapy is associated with fat weight gain (1), for people with both type 1 and type 2 diabetes. When you lower blood glucose with insulin, you keep and store all of the calories instead of losing some glucose through urine (during hyperglycemia). Unfortunately, some people skip or limit their insulin use to help them lose weight (2), but that is a dangerous practice that can lead to loss of excess muscle mass and life-threatening conditions like DKA. The best way to balance your insulin use and your body weight, in my opinion, is to be physically active to keep your overall insulin levels lower. It’s easier to lose weight, too, when you’re taking less insulin—or releasing less of your own if your pancreas still does that.
Food Choices: What you choose to eat has a huge impact on your insulin needs as well as your body weight. My graduate student found that by doing frequent dosing with his insulin pump, he was eating more overall because he could without having to take another injection with a needle. Just because insulin use can make it easier for you to eat cake and other formerly “forbidden” foods doesn’t mean that you need to eat them! There are advocates out there for all sorts of diets for people with diabetes, including ultra-low-carb ones (like Dr. Bernstein’s), vegan ones, etc. Personally, what I have always founds works best is a balanced diet. People don’t necessarily lose weight on low-carb diets, even though their insulin requirements are lower because fat is so much denser in calories (at over 9 calories/gram of fat) than carbs or protein (both 4 calories per gram). If you cut carbs out of your diet, you have to eat something in its place. It’s just too easy to overdose on fat calories without realizing it, and even when your muscles become insulin resistant for any reason, insulin still works to put fat into storage depots around the body. Don't completely avoid carbs; rather, choose them wisely—eating more carbs that are absorbed more slowly and don’t cause spikes in blood glucose that you have to try to match with large doses of insulin that often lead to hypoglycemia later. Most carbs are fully absorbed in the first hour or two after you eat them, and even rapid-acting insulin can linger for up to 8 hours afterwards. Besides, insulin requirements are determined by more than just carbs, and eating fat with the same number of carbs increases insulin requirements (3). It’s not just about carb counting anymore (and never has been for me); it’s about picking the right balance and type of carbs, as well as total amounts of protein (good for preventing lows 3 to 4 hours later) and fat (fully absorbed in 5 to 6 hours, causing insulin resistance).
Treating Lows: I was contacted once by a US Olympic team handball player with type 1 diabetes who wanted to ask me why she was gaining fat weight while doing all her training. My first question to her was, “Are you treating a lot of lows?” I knew she was going to answer yes. Gaining weight from treating lows is common in people using insulin, whether they are active or not. One of the biggest deterrents to successful weight loss and prevention of weight gain with diabetes is being forced to treat frequent bouts of hypoglycemia with glucose, sugary drinks, or food. Even though these calories are necessary to treat a medical condition, they still count as calories in the body. One way to cut back on lows is to decrease your insulin intake to prevent them, which may include decreasing meal-time insulin doses before exercise, insulin taken for food after exercise, and basal insulin doses to prevent later-onset hypoglycemia following activities. It also helps to more precisely treat lows instead of overtreating them (it’s harder to follow this advice when you’re low, though!) Immediately treat lows first with glucose—in the form of tablets, gels, or candy containing dextrose like Smarties—and then reassess later if you need additional food intake (often a mix of carbs, protein, and fat) to fully correct the low and prevent lows later on. Juice, although often touted as a treatment for hypoglycemia, contains fructose (fruit sugar) that is much, much more slowly absorbed than glucose and can lead to overtreating lows while you’re waiting for the juice to kick in. Don’t eat more calories treating a low than you need to!
Lack of Physical Movement: Finally, and I probably should have listed this section first, expending more calories can help prevent weight gain, even if you take insulin. In adults with type 1 diabetes, having an active lifestyle compared with a more sedentary one has been associated with a lower BMI (body mass index) and percentage of total and truncal fat mass (5). The more you move, the less insulin your body needs to get the same glucose-lowering effect. Requiring smaller doses of insulin allows you to 1) treat lows with fewer calories overall, and 2) avoid having as many lows from being off on your dosing. In anyone who is insulin resistant (most people with type 2 diabetes and many with type 1 who are inactive), total insulin requirements will be so much higher that there is a lot more room for error. Injected or pumped insulin is generally absorbed at a speed dictated by the dose, meaning that larger doses take longer to fully absorb and the insulin “tail” hangs around for longer. Taking or releasing less insulin due to being physically active means that all of the carbs you take will be stored as carbs in muscle or liver and not converted into fat to be stored. Stay regularly active—even if that means just standing up more or taking more daily steps--to keep your calorie expenditure high and your insulin needs low.
(1) Conway B, Miller RG, Costacou T, Fried L, Kelsey S, Evans RW, and Orchard TJ. Temporal patterns in overweight and obesity in Type 1 diabetes. Diabet Med 27: 398-404, 2010. (http://www.ncbi.nlm.nih.gov/pubmed/20536510)
(2) Ackard DM, Vik N, Neumark-Sztainer D, Schmitz KH, Hannan P, and Jacobs DR, Jr. Disordered eating and body dissatisfaction in adolescents with type 1 diabetes and a population-based comparison sample: comparative prevalence and clinical implications. Pediatr Diabetes 9: 312-319, 2008. (http://www.ncbi.nlm.nih.gov/pubmed/18466215)
(3) Wolpert HA, Atakov-Castillo A, Smith SA, and Steil GM. Dietary Fat Acutely Increases Glucose Concentrations and Insulin Requirements in Patients With Type 1 Diabetes: Implications for carbohydrate-based bolus dose calculation and intensive diabetes management. Diabetes care 36: 810-816, 2013. (http://www.ncbi.nlm.nih.gov/pubmed/23193216)
(4) Brown RJ, Wijewickrama RC, Harlan DM, and Rother KI. Uncoupling intensive insulin therapy from weight gain and hypoglycemia in type 1 diabetes. Diabetes Technol Ther 13: 457-460, 2011. (http://www.ncbi.nlm.nih.gov/pubmed/21355723)
(5) Brazeau AS, Leroux C, Mircescu H, and Rabasa-Lhoret R. Physical activity level and body composition among adults with type 1 diabetes. Diabet Med 29: e402-408, 2012. doi: 410.1111/j.1464-5491.2012.03757.x. (http://www.ncbi.nlm.nih.gov/pubmed/22817453)