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What Causes Diabetes: Is Sugar the Real Culprit?

Director Cardiology, Fortis Escorts Hospital
Jun 2, 2019 6:06 AM 4 min read

Diabetes is one of the most pervasive lifestyle diseases as we discussed last week, with an estimated prevalence of 425 million, as per the IDF Diabetes Atlas 2017. Another 350 million people are pre-diabetic, or at risk of developing diabetes in the future. It accounts for over 4 million deaths per annum worldwide, making it one of the deadliest scourges of mankind.


The Big Question However Is…What causes Diabetes?


Is it a consequence of eating too much sugar, or does sugar just happen to increase the risk of diabetes in patients who are genetically at high risk (positive family history, that is)?


There are two common types of diabetes.


Type 1 (about 5% of cases): Is caused by an absolute deficiency of insulin production in the body and thus is diagnosed during childhood.


Type 2 diabetes (over 90% of cases): Is caused by Insulin Resistance.


What is Insulin Resistance?: A condition when a greater amount of insulin is required to maintain normal blood sugar levels. Needless to say, with passage of time (about 3-15 years), many of these patients also develop a deficiency of insulin secretion due to sustained over-production.


Trend of Insulin Resistance in Humans
Source: Power-Pak C.E.


For several decades, the prevalent view among physicians was that diabetes occurred only to those at high risk, and that restriction of sugar was advisable only to those with overt diabetes.


However recently, the ill effects of sugars and sugar sweetened beverages (SSBs) have become better established. Guidelines have come up which restrict acceptable sugar consumption to 6-9 tsp per day. But, they still don’t clarify the important question asked i.e., is diabetes a consequence of eating too much sugar, or does sugar just happen to increase the risk of diabetes in patients who are genetically at high risk.


Dessert - Are desserts the culprit for diabetes?


Throughout the 20th century, numerous textbooks and journal articles have been dedicated to this critical concept. However, there was no evidence of a direct link between sugar consumption and diabetes. This was because the consumption of excess sugar is not accompanied by simultaneous rise in blood sugar for a long time. It was realized much later that this was due to the capacity of pancreas to flexibly vary the quantity of insulin released in blood, depending on the body's intake of sugar in the first place.


Different people have a different sensitivity to insulin secreted as well as the effects of sugar in diet...making any interpretation of these linkages even more elusive.


During this time, the underlying cause for diabetes was thought to be obesity. Due to the incomplete "Calories In, Calories Out" model of obesity discussed earlier here and here, fat in the diet (being the most calorie rich nutrient) was thought to be responsible for obesity, diabetes and ultimately, heart disease and strokes. This was the thought which drove the restriction of fats, as advised by dietary guidelines till 1970s.


The Answer…


A breakthrough in this field came from Gerald Reaven, a leading American endocrinologist. Dr Reaven had been studying Insulin Resistance since 1968. In his classic Banting Lecture of 1988, he gave the conceptual framework to understand the precursor for major lifestyle diseases. Referred to as the “Metabolic Syndrome” (also called Syndrome X or Reaven’s Syndrome), this comprised a set of conditions that included:


  • Upper body or abdominal obesity
  • High blood pressure
  • High serum triglycerides
  • Low HDL-cholesterol levels 
  • High blood sugars


The presence of any 3 of these 5 criteria confirmed the diagnosis. The underlying abnormality was established to be Insulin Resistance.


An inability to change one’s lifestyle significantly was postulated to be a possible cause for worsening of these conditions ultimately leading to full-blown diabetes, hypertension, heart disease and strokes.


This discovery also appears to tie up the underlying abnormalities between obesity, diabetes and heart disease, namely, insulin resistance, which appears to be common to all of them.


Further, we now know that the body responds to different dietary nutrients differently. Carbohydrates are associated with early taste satisfaction but result in a craving for frequent meals/snacking, while proteins and fats grant greater satiety, keeping one full for a longer duration.


Thereby, excess refined carbohydrates in the diet, especially sugars is the driver for chronic overeating and obesity leading to insulin resistance (due to the repeated cycles of excess insulin secretion following frequent carb-based meals) and its sequelae - diabetes, hypertension, lipid abnormalities, heart disease and strokes.


A large meta-analysis in 2015 finally reported that high consumption of SSBs, artificially sweetened beverages and fruit juices are all associated with new-onset diabetes, independent of the body weight (though individuals already overweight/obese were at higher risk). However, the data for sugar (i.e., SSBs) was more convincing than the other two groups.


In summary, sugar and refined carbohydrates in the diet are associated with excess release of insulin in the body leading to insulin resistance, which is a precursor to the development of the lifestyle diseases, such as, obesity, high blood pressures, abnormal lipid levels, diabetes, heart disease and strokes. While there is no direct one to one correlation between sugar intake and diabetes, the presence of excess sugar in our diet has undoubtedly increased the risk of developing insulin resistance, that appears to be the common metabolic abnormality underlying these conditions.



This is part of a recurring column series published every Sunday. Click here to view my other articles on health, nutrition and exercise.