What is the relationship between insulin sensitivity and weight loss?
Insulin resistance and obesity are both symptoms of type 2 diabetes, although they also occur at a prediabetic stage, before the diabetes diagnostic criteria are met. Insulin resistance is highly predictive of diabetes. In the Bruneck study, less than 10% of the insulin resistant subjects had no other metabolic disorder. But still, the exact relationship between insulin resistance and obesity is unclear, as they could
- have a common cause, or
- one of them causes the other, or
- be coupled in a positive feedback cycle, or
- all of the above. But we know that they are highly correlated in untreated patients.
This is the prevalence of insulin resistance in adolescents from NHANES, with white circles denoting normal weight adolescents, black squares denoting overweight adolescents and black circles denoting obese adolescents.
For example, one of the theories for the progression to diabetes is that the capacity of the body's usual fat depots is overtaxed, leading to having too much fat where it does not belong (e.g. intraabdominal fat deposits), resulting in lipotoxicity and finally diabetes. This would be a potential argument for obesity leading to insulin resistance. A common cause could be searched e.g. in reduced incretin secretion or increased JNK activity. But given the difficulty of finding a clear mechanism, and the complexity of the pathways involved, the connection is probably multifactorial.
Weight loss is one of the goals in diabetes management. Exercise and dieting delay the progression of prediabetic stages to diabetes. They reduce both obesity and insulin resistance. So, to answer your question directly, if you had insulin resistance, and you managed to lose weight, it is very likely that your insulin sensitivity has increased.
The above assumes that the patient is not taking any metabolic treatment. If he is taking diabetes medications, their effect on insulin sensitivity and weight will be independent. Some medication classes like GLP 1 agonists will reduce both obesity and insulin related effects, as will bariatric surgery. Metformin will improve insulin sensitivity without affecting weight much, while the glitazones reduce insulin resistance but lead to weight gain.
People who have insulin resistance generally find it more difficult to attain and maintain a healthy weight.
If the person with insulin resistance is overweight (which is often the case), and if s/he succeeds in losing even a small amount of weight, s/he will generally see some immediate improvement in their insulin sensitivity and a lessening of symptoms (such as headache, yucky feeling, foggy feeling).
A low-carb diet helped my insulin resistant son.