Copyright © 2009
by Daniel Matthew Korn

All Rights Reserved

Stress, hunger, sleep deprivation, and impaired fat metabolism are often overlooked predictors of obesity. In this chapter, we shall look at some of the diseases related to obesity that have been the focus of medical efforts. Obesity is a risk factor for many diseases and, directly or indirectly, obesity and many chronic diseases share the same causes. Looking at the research on some of the chronic diseases that occur more frequently in obese people may shed some light on their common causes.

Heart Disease

There are several forms of heart disease. The main type is coronary artery disease. It is also known as ischemic heart disease and involves an interruption to the blood supply. This condition leads to heart attack, also known as myocardial infarction, and death. Only a century ago, the majority of deaths in the United States were caused by infectious diseases. Today, the number one cause of death in the United States is coronary artery disease. It kills half a million people a year in the United States, almost equivalent to the population of Washington, D.C.

Obesity is a known risk factor for heart disease and high cholesterol, and it also leads to heart attacks at younger ages. A study published in the Journal of the American College of Cardiology looked at over 111,000 people who had suffered heart attacks and found that on average the most obese patients had their first heart attack at age 59. The leanest patients had their first heart attack at age 75.¹ High cholesterol, especially LDL cholesterol, which is known as the “bad” cholesterol, is the usual suspect in heart disease. In fact, the mechanism by which heart attacks occur involves a build-up of cholesterol along an artery wall, which then ruptures and blocks the artery. The general assumption has been that a diet high in animal fat, which contains cholesterol, leads to heart disease and weight gain. There are some problems with this theory. As we have already mentioned, the Inuit and the French eat much more animal fat than do Americans but have lower rates of heart disease.

Cholesterol levels do not predict all heart attacks. Almost half the people who experience heart attacks have normal blood cholesterol levels. A 2002 study in The New England Journal of Medicine found that inflammation levels, as measured by a marker called C-reactive protein, were a 40% better predictor of heart disease than LDL “bad” cholesterol. Another study, which followed almost 28,000 people for eight years, found that inflammation was able to predict heart disease twice as well as could LDL cholesterol. Inflammation seems to contribute to heart disease by causing an increase in unstable cholesterol deposits along arterial walls. The idea that inflammation is a cause of heart disease is now generally accepted.^2,3

There is also evidence that cholesterol levels may not be so strongly connected to obesity as previously thought. A ten-year study in the United States of almost 1,700 individuals showed improving cholesterol profiles and increasing obesity occurring at the same time.⁴ This means lowering cholesterol does not necessarily lead to weight loss, and weight gain may not result in an increase in cholesterol.

Several low carbohydrate diet books have proposed that refined carbohydrates are the cause of the modern increase in chronic disease. However, refined carbohydrate consumption is much higher in Thailand and Bangladesh than in the United States. This theory does not explain the low rate of heart disease in those countries.

Stroke

As with heart disease, there is more than one type of stroke. However, about 80% of strokes are ischemic strokes. Just as ischemic heart disease involves an interruption of blood supply to the heart, ischemic stroke involves an interruption of blood supply to the brain, which causes cell death. High blood pressure, a condition associated with obesity, is a major risk factor for stroke. Other risk factors include inflammation,⁵ diabetes and smoking. High cholesterol is a risk factor for stroke but of lesser significance than in heart disease. Taking cholesterol-lowering statin drugs has been shown to reduce strokes by only about 15%.⁶

Obesity is a risk factor for stroke. A six-year study of middle-aged adults found that women who were obese, as measured by BMI, had roughly three times as many strokes as did women of normal weight. The study found that obese men had about 10% more strokes than did men of normal weight. While this seems to show that obesity causes more strokes among women than among men, it may simply reflect that BMI is a better measure of body fat for women than men. BMI does not measure whether above average weight is due to fat or muscle, so there may be athletic men in this study who have been incorrectly classified as obese.⁷

Diabetes and Pre-diabetes

Glucose, or blood sugar, is an energy source for the cells in our bodies. Insulin is a hormone that tells our cells to take in glucose from the blood. After we eat a meal, our blood sugar rises above normal levels and insulin is released to bring blood sugar levels back to normal. Diabetes is a disorder of this process. In type 1 diabetes, the body does not produce insulin. People with type 1 diabetes need to give themselves injections of insulin. The most common form of diabetes is type 2. In type 2 diabetes, the body can still produce insulin but its cells do not respond properly to insulin’s signal to take glucose from the blood. This results in increased hunger and is called insulin resistance.⁸ It has long been known that type 1 diabetes occurs because the immune system incorrectly attacks insulin-producing cells in the pancreas. Inflammation, which is an immune system process, has recently been implicated as the cause of type 2 diabetes and insulin resistance.⁹

Insulin resistance results in a loss of blood sugar control and high blood sugar levels that do not return to normal after meals. This is known as hyperglycemia. It also occurs in pre-diabetes, which can be a precursor to type 2 diabetes. In pre-diabetes, blood sugar is elevated, but not to the levels in type 2 diabetes. It is estimated that about 23 million Americans have type 2 diabetes and that six million of these cases are undiagnosed. An additional 56 million Americans are thought to have pre-diabetes, of which many more are undiagnosed. Of those people with type 2 diabetes, 55% are obese.^9,10 Obesity has traditionally been looked at as a risk factor for diabetes and insulin resistance. However, the opposite appears to be the case; a recently published ten-year study found that insulin resistance predicted weight gain. Nine and ten-year-olds of normal weight who were developing insulin resistance were more likely to become overweight young adults.¹¹ Insulin resistance causes increased hunger, and increased hunger leads to weight gain.

Connecting the Weight Gain Risk Factors

Obese people are more likely than people of normal weight to be diagnosed with many additional diseases, most of which are connected to the body’s immune system and excess inflammation. This is the link among stress, sleep deprivation, excess hunger, and chronic disease. Stress has long been known to be a risk factor for sudden heart attack. Stressful situations, including natural disasters and wars, are associated with higher occurrences of heart attacks.¹² As we have seen, inflammation is an even greater predictor of heart attack than is cholesterol level, and emotional stress increases inflammation as well as blood pressure.¹³ Sleep deprivation also causes increases in stress, and even one night of sleep deprivation is associated with an increase in inflammation levels.¹⁴ We have already seen that insulin resistance predicts weight gain, and insulin resistance is an inflammatory disease. Increased hunger is a symptom of insulin resistance and type 2 diabetes. The failure of insulin to move sugar into cells causes muscles and organs to become energy deficient and triggers intense hunger, which is a cause of weight gain.¹⁵

While all of these factors seem to be connected, it is not yet clear how they are related to the heightened LDL “bad” cholesterol observed in obesity and associated diseases. Some studies have shown minor increases of cholesterol in response to stress, but stress does not account for the huge increases in cholesterol levels seen in the twentieth century. However, since all of these symptoms are occurring together, it is probable that they have causes in common. Now that we have identified a variety of factors associated with weight gain, it is time to evaluate the possible causes.

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Citations:

¹ Mohan C. Madala and others. "Obesity and Age of First Non–ST-Segment Elevation Myocardial Infarction." Journal of the American College of Cardiology. 7/26/2009 http://content.onlinejacc.org/cgi/content/abstract/52/12/979.

² Paul M. Ridker and others. "Comparison of C-Reactive Protein and Low-Density Lipoprotein Cholesterol Levels in the Prediction of First Cardiovascular Events." New England Journal of Medicine. 7/26/2009 http://content.nejm.org/cgi/content/full/347/20/1557.

³ Ray Hainer. "The cholesterol-inflammation connection." CNN. 8/09/2009 http://edition.cnn.com/2008/HEALTH/conditions/10/16/healthmag.cholesterol.inflammation/index.html.

⁴ Kathleen Blanchard. "U.S. Cholesterol Profiles Improve While Obesity Persists." Emax Health. 8/09/2009 http://www.emaxhealth.com/1020/107/29268/us-cholesterol-profiles-improve-while-obesity-persists.html.

⁵ E. Van Exel and others. "Inflammation and stroke: the Leiden 85-Plus Study." PubMed. 8/09/2009 http://www.ncbi.nlm.nih.gov/pubmed/11935072.

⁶ C. O'Regan and others. "Statin therapy in stroke prevention: a meta-analysis involving 121,000 patients." PubMed. 8/09/2009 http://www.ncbi.nlm.nih.gov/pubmed/18187070.

⁷ Wayne Kuznar. "Obesity Associated With Increased Stroke Risk in Middle-Aged Women." Quadrant HealthCom Inc. 8/09/2009 http://www.neurologyreviews.com/08apr/ObesityStroke.html.

⁸ H. P. Himsworth (1936). "Diabetes Mellitus: its differentiation into insulin-sensitive and insulin-insensitive types." Lancet 1: 127–130

⁹ "Type 2 Diabetes: Inflammation, Not Obesity, Cause of Insulin Resistance." Science News. 8/09/2009 http://www.sciencedaily.com/releases/2007/11/071106133106.htm.

¹⁰ Paul S. Jellinger. "What You Need to Know about Prediabetes." Power of Prevention, American College of Endocrinology. Vol. 1, issue 2, May 2009.

¹¹ "Overweight, Obesity & Weight Loss." American Diabetes Association. 8/09/2009 http://www.diabetes.org/diabetes-research/summaries/overweight.jsp.

¹² J. A. Morrison and others. "Pre-teen insulin resistance predicts weight gain, impaired fasting glucose, and type 2 diabetes at age 18-19 y: a 10-y prospective study of black and white girls." PubMed. 8/09/2009 http://www.ncbi.nlm.nih.gov/pubmed/18779296.

¹³ J. S. Chi and R. A. Kloner. "Stress and myocardial infarction." PubMed Central. 8/09/2009 http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1767636.

¹⁴ Kathryn E. Wellen and Gökhan S. Hotamisligil. "Inflammation, stress, and diabetes." Journal of Clinical Investigation. 8/09/2009 http://www.jci.org/articles/view/25102.

¹⁵ "Loss Of Sleep, Even For A Single Night, Increases Inflammation In The Body." ScienceDaily. 8/09/2009 http://www.sciencedaily.com/releases/2008/09/080902075211.htm.

¹⁶ "Type 2 Diabetes: Symptoms." Mayo Clinic. 8/09/2009 http://www.mayoclinic.com/health/type-2-diabetes/DS00585/DSECTION=symptoms.