A lot of people with type 2 diabetes delay going on insulin for as long as possible because they’ve heard horror stories about how much weight it can make them gain (or maybe they just don’t like shots), but people with type 1 don’t have a choice. While it is true that insulin treatment is often associated with weight gain and more frequent bouts of hypoglycemia (low blood sugar), the real question is, why?
Some theories to explain insulin-induced weight gain are that when using insulin, your blood sugar is (usually) better controlled and you stop losing some of your calories (as glucose in your urine when your blood sugars exceed your urinary threshold) and that you may gain weight from having to eat extra to treat any low blood sugars caused by insulin. If you’re taking oral medications to lower your blood sugar and they are not working, however, insulin may be your main option for better control.
A few research studies have looked at whether weight gain is simply a result of eating more when you’re on insulin. One such study found that weight gain was not due to an increase in food intake, but rather that your body may increase its efficiency in using glucose and other fuels when your glycemic control improves—making you store more available energy from the foods you eat as fat (even if you’re eating the same amount as before you went on insulin) (1).
So, what can you do to avoid weight gain if you have to take insulin? First of all, you should try to keep your insulin doses as low as possible because the more insulin you take, the greater your potential for weight gain is. The best way to keep your insulin needs in check is to engage in regular physical activity. By way of example, some people with type 2 diabetes who were studied gained weight from insulin use while others did not. Interestingly, the main difference between the “gainers” and the “non-gainers” was that the gainers were less physically active (2). Moreover, in people with type 1 diabetes, taking insulin doses that effectively manage blood sugars can also lead to weight gain, but increases in activity levels have been shown to prevent getting fatter (3).
During any physical activity, your muscles can take up blood glucose and use it as a fuel without insulin and then following exercise, your insulin action is heightened for a few hours and as long as 72 hours—meaning that you will need smaller doses of insulin to have the same glucose-lowering effect. It is my personal experience that regular exercise is the best way to prevent insulin-induced weight gain, but your insulin doses will also need to be adjusted downward to prevent low blood sugars that cause you to take in extra calories to treat them.
Second, you may be able to avoid weight gain by taking a look at the type of insulin(s) that you are using. For example, in overweight type 2 diabetic subjects, use of once-daily Levemir (detemir) caused less weight gain and less frequent hypoglycemia than use of NPH (4), even combined with use of rapid-acting injections of a separate insulin for meals (and the same is likely true when using Lantus, or insulin glargine). Anyone taking basal insulin alone (once or twice daily) or following a basal-bolus regimen can benefit by making sure that insulin doses are regulated effectively to prevent blood sugar lows and highs—while using as little insulin as absolutely necessary to get the desired glycemic effect.
In other words, the type of insulin you use and the doses you take are both important to consider in the overall management of your diabetes and your body weight, regardless of which type you have. Just as importantly, though, is how you choose to manage your lifestyle, both your exercise and your dietary choices. Changes in your lifestyle, such as cutting back on refined carbohydrates that require larger doses of insulin to cover them and exercising regularly, are likely your best bets to counteract any potential weight gain caused by insulin use. An added side benefit is that if you have type 2 diabetes and start exercising regularly, you may actually lose fat weight and be able to lower your insulin doses more or get off of insulin injections completely.
- Jacob AN et al. Weight gain in type 2 diabetes mellitus. Diabetes Obes Metab. 2007 May;9(3):386-93.
- Jansen HJ et al. Pronounced weight gain in insulin-treated patients with type 2 diabetes mellitus is associated with an unfavourable cardiometabolic risk profile. Neth J Med. 2010 Nov;68(11):359-66.
- Jacob AN et al. Potential causes of weight gain in type 1 diabetes mellitus. Diabetes Obes Metab. 2006 Jul;8(4):404-11.
- Fajardo Montañana C et al. Less weight gain and hypoglycaemia with once-daily insulin detemir than NPH insulin in intensification of insulin therapy in overweight Type 2 diabetes patients: the PREDICTIVE BMI clinical trial. Diabet Med. 2008 Aug;25(8):916-23.