The Physiology of Type 2 Diabetes

The power of a plant-based diet is a wonderful tool for those who have the constellation of diseases directly tied to type 2 diabetes – hypertension, obesity, and heart disease.  These are all tied together by a common abnormality of physiology.[i] The primary connection between these diseases is a high insulin level. 

Excessive insulin:

  • causes growth of muscle cells
  • causes growth of fat cells, the intra-abdominal collection being the worst
  • promotes LDL cholesterol production and represses the good HDL cholesterol, resulting in an increased risk of heart disease.
  • increases sodium retention in the kidneys; this may be at least partly responsible for the strong association between insulin and hypertension.


[1] Reaven GM. Banting Lecture 1988. Role of insulin resistance in human disease.  Diabetes. 1988 Dec;37(12):1595-607. PMID: 3056758

The Causes of Excess Insulin and Inflammation

The cause of high insulin levels is basically taking in too many calories, more than the body needs to function.  Refined carbohydrates (sugars) likely create the fastest rise in insulin. But excess insulin production can also be stimulated by amino acids (protein building blocks) such as arginine and others.  On the other hand, fat calories work more slowly to raise insulin by creating an insulin resistance from within the cell.  This makes it difficult for the cell to take in sugars, which leaves sugar circulating in the blood. The rising blood sugar then makes the body produce more insulin.2

 High sugar and insulin promote inflammation.[i]   The inflammation coming from intra-abdominal fat is the most destructive and not only accelerates the blood vessel damage of heart disease and hypertension but also increases the risk of cancer, osteoarthritis, dementia and other inflammation-related diseases.

[i] Giacco F, Brownlee M. Oxidative stress and diabetic complications. Circ Res. 2010;107(9):1058–1070. doi:10.1161/CIRCRESAHA.110.223545

Steps in the Development of Type 2 Diabetes

The development of type 2 diabetes starts out with muscle (and other tissues) insulin resistance.[i]  This raises the total body insulin levels.  At this stage, although it may be taking the body longer to push sugar into the body cells, the system is able to maintain normal fasting blood sugars.  Only the elevated blood pressure, cholesterol, and/or weight are evidence of the underlying problem. 

Another of the steps in the development of type 2 diabetes resides in the liver.  One of the liver’s jobs is to make sugar for the body to use when there are no calories coming in (the fasting state).  Insulin normally tells the liver to stop making sugar once breakfast begins but when the liver develops insulin resistance from excessive calorie intake it does not stop the liver from pouring even more sugar into the system.   It is at this point that the fasting sugars start moving upward and the doctors diagnose diabetes.  It should be noted that the underlying process of excessive calories and insulin may go on for years before the blood sugars rise and the diagnosis is actually made.

 Fat may also raise sugar levels by “plugging up” the energy-producing Kreb’s cycle and creating a buildup of glucose in the cell.  This keeps “new” sugar from entering the cell and raises the blood sugar as well.  So you see, Type 2 diabetes has more to do with excess calories than simply excess sugar.

 A frequent source of excessive calories, alcoholic drinks, also impacts the liver. The ethanol is quickly changed by the liver into fat which is stored in that organ as well as other abdominal tissues, hastening the development liver insulin resistance and the production of the inflammatory cytokines that accompany type 2 diabetes.  Hence the term, “beer belly,” used by many in recognition that excessive alcohol leads to larger abdominal girth. 

 What follows is a broadening of the negative effects of high sugar, high insulin, and inflammation on body organs, including the lining of the blood vessels.  Together these all add up to the pathologies associated with type 2 diabetes – heart attacks, strokes, blindness, kidney failure, neuropathy, and amputations.  Associated diseases such as gastrointestinal reflux disease, osteoarthritis, sleep apnea, gout, depression and others are also accelerated.


[i] Olefsky JM, Nolan JJ. Insulin resistance and non-insulin-dependent diabetes mellitus: cellular and molecular mechanisms. Am J Clin Nutr 1995;61(suppl):980S-6S.

Is It Genetics?

While there is a genetic component to the disease[i] the epigenetic effect is capable of overriding it in most cases.[ii]  Epigenetics is the study of how our behaviors and environment can change the expression of the genes, i.e. turn the genes off or on.  My first exposure to this concept was the report of a study in Finland in which biopsies of abdominal fat were done in individuals who had been diagnosed with pre-diabetes.[iii]  The individuals were then randomly placed on either a rye and pasta or an oat, wheat, and potato diet for 12 weeks.  The abdominal fat was then biopsied again and the genetic expression was reassessed.   It was fascinating to see that those on the rye-pasta diet had their genes move away from diabetes while those on the oat-wheat-potato diet had their gene expression move toward diabetes.

[i] Scott RA, Fall T, Pasko D, et al. Common genetic variants highlight the role of insulin resistance and body fat distribution in type 2 diabetes, independent of obesity. Diabetes. 2014;63(12):4378–4387. doi:10.2337/db14-0319

[ii] Chacko SA, Sul J, Song Y, et al. Magnesium supplementation, metabolic and inflammatory markers, and global genomic and proteomic profiling: a randomized, double-blind, controlled, crossover trial in overweight individuals. Am J Clin Nutr. 2010;93(2):463–473. doi:10.3945/ajcn.110.002949

[iii] Kallio P, Kolehmainen M, Laaksonen DE, et al.  Dietary carbohydrate modification induces alterations in gene expression in abdominal subcutaneous adipose tissue in persons with the metabolic syndrome: the FUNGENUT Study. Am J Clin Nutr 2007;85:1417–27.

Reversibility and Remission

The whole experience from pre-diabetes through death is one of discomfort and disease.  But, in most cases, it is completely avoidable.  Less “advanced” cultures have much less of this disease and there are populations where it is almost nonexistent.  An instructive example is that of the Pima Indians.[i]  Several hundred years ago the Pima Indians were divided between Mexico and the Hila River Basin in Arizona (USA).  In a recent study of the two populations a very low incidence of diabetes was noted in the Mexican side of the tribe while those in Arizona had a 38% incidence.   There was no significant difference in the basic genetic pool between the two groups. However, because of lifestyle habits, the genes responsible for diabetes were basically turned off in those residing in Mexico.

The first strong scientific evidence for the reversal of type 2 diabetes came from the bariatric surgeons..[ii],[iii],[iv]  The medical reversal was clearly documented by Roy Taylor’s group in the UK in the Counterpoint study.[v]  He demonstrated that 8 weeks on 600 kcal per day of non-starchy vegetables was adequate to remove the extra fat from both the pancreas and the liver and return the function of both to normal.   Weight came down and sugars returned to normal.  Not only that but inflammation also dramatically improved.  We can now speak much more freely about diabetes reversal.

 In 2018 the first yearly report of the DiRECT trial was published in which a group of primary care offices applied the knowledge gained in the Counterpoint study to people in communities across the UK. [vi]  Calories were limited to just over 800 kcal with the goal of losing 15 kg.   Eighty-six percent of those who lost the 15 kg had complete reversal of their type 2 diabetes as defined by a normal A1C and using no medication for 3 months.

This provides significant hope for those with any of the high-insulin-related diseases.  While there are parts of the disease that are not reversible (we cannot rebuild a kidney or regrow an amputated limb), it is encouraging to know that there can be improvement and even reversal to many of the associated problems like those effecting the heart,[vii] eyes,[viii] nerves,[ix],[x] and kidneys.[xi] The earlier a reversal program is started in the long path of the disease, the better the outcome; this is true even in the stage where blood sugar has not yet been raised.


[i] SCHULZ LO, BENNETT, RAVUSSIN E. Effects of Traditional and Western Environments on Prevalence of Type 2 Diabetes in Pima Indians in Mexico and the U.S. DIABETES CARE, VOLUME 29, NUMBER 8, AUGUST 2006

[ii] Carlsson LM, Peltonen M, Ahlin S, et al. Bariatric surgery and prevention of type 2 diabetes in Swedish obese subjects. N Engl J Med 2012;367:695–704

[iii] Sjo ̈holm K, Anveden A, Peltonen M, et al. Evaluation of current eligibility criteria for bariatric surgery: diabetes prevention and risk factor changes in the Swedish obese subjects (SOS) study. Diabetes Care 2013;36:1335–1340 32.

[iv] Sjo ̈stro ̈m L, Gummesson A, Sjo ̈stro ̈m CD, et al.; Swedish Obese Subjects Study. Effects of bariatric surgery on cancer incidence in obese patients in Sweden (Swedish Obese Subjects Study): a prospective, controlled intervention trial. Lancet Oncol 2009;10:653–662

[v] Taylor R. Banting Memorial lecture 2012: reversing the twin cycles of type 2 diabetes. Diabet Med. 2013 Mar;30(3):267-75. doi: 10.1111/dme.12039

[vi] Lean MEJ, et al.  Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial Lancet 2018; 391: 541–51

[vii] Ornish D, et al Intensive lifestyle changes for reversal of coronary heart disease  Five-year follow-up of the Lifestyle Heart Trial.  JAMA. 1998;280:2001-2007.   

[viii] Kempner W, Lohmann R, Schlayer C. Effect of Rice Diet on Diabetes mellitus Associated with Vascular Disease.  Post Graduate Medicine, October, 1958. P. 359-371.

[ix] Crane MG, Sample C. Regression of diabetic neuropathy with total vegetarian (Vegan) diet. J Nutr Med 1994; 4: 431–439.

[x] Bunner AE, Wells CL, Gonzales J, et al. A dietary intervention for chronic diabetic neuropathy pain: a randomized controlled pilot study. Nutr Diabetes 2015; 5: e158

[xi] Fioretto PBarzon IMauer M.  Is diabetic nephropathy reversible? Diabetes Res Clin Pract. 2014 Jun;104(3):323-8. doi: 10.1016/j.diabres.2014.01.017. Epub 2014 Jan 20.

What About Type 1 Diabetes?

It should be noted here that not all diabetes is type 2.  The type 1 diabetes is caused primarily by a loss of the ability of the β-cells of the pancreas to make insulin. The β-cells in the pancreas which make insulin are usually destroyed by the immune system or a toxin.   This type of diabetes is not reversible, and requires lifelong insulin therapy.  However, the stability of the disease is much better when following the same lifestyle that leads to reversal of type 2 diabetes.


 The purpose of this cookbook is to assist you in moving toward a diet and lifestyle that restores health and may, when applied carefully, even reverse chronic disease.  This chapter has been a short review of what we know about type 2 diabetes and its associated diseases. While it is not exhaustive, it should provide enough evidence that you can have confidence that what has been recommended is supported by the science. 

 Experience also teaches us that those who make the change to a plant-based diet feel healthier and happier, and have more energy and clarity of mind.  Many think they “eat what they like” but science teaches us that we “like what we eat.”   That is, taste buds are trainable.  And, if indeed they are, then shouldn’t we choose that which will bring us the greatest health and happiness?   I would encourage you to move toward embracing minimally processed, whole, plant-based foods.

 To your health,

 George E Guthrie, M.D., M.P.H., C.D.C.E.S., F.A.A.F.P., F.A.C.L.M.

George Guthrie’s Eat Plants Feel Whole is a treasure trove of nutritional information and lifestyle guidance toward an ultimate journey of optimal health without chronic illness.

— Caldwell B. Esselstyn, Jr., Md,
Author of Prevent and Reverse Heart Disease