Diabetes is a continuum, starting as pre diabetes as many as 10 years before its diagnosis. Whilst fasting glucose and oral glucose tolerance tests can be effective tools for measuring blood glucose, and glucose response, they only provide us with half of the picture.
The type 2 diabetes continuum begins as a patient becomes overweight. As insulin resistance develops, endogenous insulin production increases. Over time, this leads to inflammation, oxidative stress, and eventually pancreatic beta cells begin to fail, however, blood glucose levels may still be within the normal range because in the early stages of pre diabetes, the pancreatic beta cells have increased their insulin production to compensate for the body’s insulin resistance. Therefore, there is an early window for intervention that is all too often, missed.
Gold standard pre diabetic testing is a 2 hour fasting oral glucose tolerance test with insulin. The elevated insulin response is the first sign of insulin resistance and pre diabetes.
Managing Insulin Resistance and Type 2 Diabetes
One of the largest studies of patients who were obese and pre diabetic found that intensive lifestyle modification (diet counselling and exercise) were far less likely to develop diabetes in three years than those in offered either standard lifestyle recommendations plus a placebo or metformin. Specifically, exercise increases muscle uptake, independent of insulin and increases muscle sensitivity to insulin. At least 30 minutes of moderate intensity physical activity per day are recommended.
With regards to diet, a 2013 meta-analysis of 20 RCTs found that low carbohydrate, low GI Mediterranean and high protein diets are all effective in decreasing HbA1c, with a Mediterranean diet showing the largest effect.
I recommend using a fasting 2-hour oral glucose tolerance test, with insulin for patients ‘at risk’ of developing diabetes. Post load levels of insulin higher than 80mU/L, and/or fasting insulin at 10-14mU/L is indicative of insulin resistance. Patients presenting with insulin resistance would benefit from an intensive lifestyle intervention program.
1. Del Prato, S. et al. (1994) Effect of sustained physiologic hyperinsulinaemia and hyperglycaemia on insulin secretion and insulin sensitivity in man. Diabetologica, 37(10):1025-1035.
2. Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine, February 7, 2002.
3. Stanfors, K. I. et al. Goodyear Advances in Physiology Education. Published 1 December 2014. Vol. 38 no. 4, 308-314.
4. National Institute of Heath, National Heart, Lung and Blood Institute. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Executive Summary.
5. Ajala, O. et al Systematic review and meta-analysis of dfferent dietary approaches to the management of type 2 diabetes. Am J Clin Nutr 2013;97:505-516
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