POST SUMMARY: What this means for you…
If you suspect you have insulin resistance, or may someday, you need to scrutinize the type and amount of carbohydrates you’re eating. Try replacing the starchiest (e.g. bread) with natural fatty foods (e.g. an egg or avocado, or a handful of olives). Start with breakfast. Start today. If you’re still afraid of dietary fat (many are), just keep telling yourself “fat doesn’t increase insulin!”
Spoiler Alert: It’s All About The Fat
Through a number of blog posts, I highlight several causes of insulin resistance, including inflammation, oxidative stress, genetics, etc. But the elephant in the room is the food we eat. Food is the culprit and the cure; whether it’s the culprit or the cure depends on whether it increases or decreases insulin, respectively.
Once we appreciate that too much insulin causes insulin resistance, we must consume foods that help keep insulin in control. Dietary protein elicits a mild insulin effect (about 2-3 times above normal), carbohydrate (depending on the carbohydrate) can elicit a remarkable increase in insulin (>10 times above normal), while dietary fat elicits no effect at all. Thus, a diet that restricts the insulin spiker (carbohydrate) and increases the insulin dampener (fat) is one that will improve insulin sensitivity.
Over the millennia that passed from early man until now, the greatest change in eating came from the establishment of agriculture and the subsequent shift in nutrients from a diet high in fat to one high in carbohydrate.
Restricting carbohydrates was perhaps the first modern documented intervention to control diabetes and weight and was accepted as fact throughout Western Europe in the early and mid 1800’s. Why such a paradigm fell out of favor and was replaced with the current recommendations that those with insulin resistance and type 2 diabetes avoid fat and eat starches like wheat and rice is a historical issue, but the shift in guidelines was dramatic.
Within decades (from the early to the mid 1900’s), guidelines for diabetics went from encouraging strict avoidance of bread, cereals, sugar, etc. while allowing any meats, eggs, cheese, etc. (per The Practice of Endocrinology in 1951), to just the opposite—encouraging breads and cereals while discouraging meats, eggs, etc. (per the American Heart Association and American Diabetes Association).
And we responded… We eat relatively less fat now than perhaps ever before and certainly less than we ate 50 years ago .
The Explosion of Insulin Resistance
The explosion of insulin resistance at home and abroad is evidence that the dietary shift has not yielded the intended results. Clinical research over the last few decades has provided abundant evidence that carbohydrate restriction is a superior dietary intervention to prevent or improve insulin resistance.
Indeed, when comparing studies that are intervention or clinical based, rather than prospective or questionnaire based, the consensus is overwhelmingly supportive of carbohydrate restriction. Intervention-based studies are far superior because they’re able to definitively answer questions, such as “which diet is best for improving insulin resistance?”
One study that asked this question brought in hundreds of overweight middle-aged men and women. For two years, study subjects were assigned to one of three diets:
- a calorie-restricted low-fat diet
- a calorie-restricted moderate-fat diet
- a non-calorie-restricted low-carbohydrate diet
In addition to causing the greatest weight loss, the non-restricted low-carbohydrate diet also helped lower insulin and improve insulin resistance the most .
A different study employed a similar strategy for 3 months, wherein overweight men and women were split into either a low-carbohydrate or low-fat diet group, both calorically non-restrictive. While insulin levels dropped by roughly 15% in the low-fat diet group, subjects in the low-carbohydrate diet group saw insulin levels drop by 50% .
Moreover, the HOMA score, an index of insulin resistance, dropped over three times more with the low-carbohydrate diet compared to the low-fat diet.
One final study worth mentioning followed study subjects for almost four years while they adhered to a carbohydrate-restricted diet . The thrust of the study was to compare metabolic improvements, including insulin sensitivity, with two interventions—diets containing either 50% or 20% carbohydrate. Not only was the lower carbohydrate diet “significantly superior” at improving health, it ultimately led to almost half of the patients getting off insulin (and almost entirely off any other medications) and the rest substantially reduced daily insulin requirements. A final study worth mentioning here is one that put insulin-resistant subjects on a relatively normal diet (~60% carbohydrate) or restricted with carbohydrates (~30%) for three weeks then switched over to the other diet for another three weeks. Insulin sensitivity increased more with the lower-carbohydrate diet .
The Scientific Proof Is Clear
There are many, many more studies that indicate similar results establishing the efficacy of diets low in carbohydrates to remarkably improve insulin sensitivity. To help sum up this fact, multiple meta-analyses that pool the findings from dozens of studies, encompassing thousands of patients, unanimously reveal that a carbohydrate-restricted, calorie-unrestricted diet lowers insulin at least as much and often more than low-fat, calorie-restricted diets [6, 7].
1. Centers for Disease C, Prevention: Trends in intake of energy and macronutrients–United States, 1971-2000. MMWR Morbidity and mortality weekly report 2004, 53:80-82.
2. Shai I, Schwarzfuchs D, Henkin Y, Shahar DR, Witkow S, Greenberg I, Golan R, Fraser D, Bolotin A, Vardi H, et al: Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. The New England journal of medicine 2008, 359:229-241.
3. Volek JS, Fernandez ML, Feinman RD, Phinney SD: Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome. Progress in lipid research 2008, 47:307-318.
4. Nielsen JV, Joensson EA: Low-carbohydrate diet in type 2 diabetes: stable improvement of bodyweight and glycemic control during 44 months follow-up. Nutrition & metabolism 2008, 5:14.
5. Garg A, Grundy SM, Unger RH: Comparison of effects of high and low carbohydrate diets on plasma lipoproteins and insulin sensitivity in patients with mild NIDDM. Diabetes 1992, 41:1278-1285.
6. Hu T, Mills KT, Yao L, Demanelis K, Eloustaz M, Yancy WS, Jr., Kelly TN, He J, Bazzano LA: Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors: a meta-analysis of randomized controlled clinical trials. American journal of epidemiology 2012, 176 Suppl 7:S44-54.
7. Santos FL, Esteves SS, da Costa Pereira A, Yancy WS, Jr., Nunes JP: Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obes Rev 2012, 13:1048-1066.
This blog post (and all other posts and content on this website) is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.
About Benjamin Bikman, Ph.D. – Ben earned his Ph.D. in Bioenergetics and was a postdoctoral fellow with the Duke-National University of Singapore in metabolic disorders. Currently, his professional focus as a scientist and professor (Brigham Young University) is to better understand chronic modern-day diseases, with special emphasis on the origins and consequences of obesity and diabetes. He frequently publishes his research in peer-reviewed journals and presents at international science meetings.