Copyright © 2009
by Daniel Matthew Korn

All Rights Reserved

One item in our diet that can cause increases in cortisol production, stress, hunger, inflammation, insulin resistance, blood pressure, blood sugar, and sleep disturbances is caffeine. Some studies have suggested that caffeine contributes to obesity.¹ While we usually think body weight is affected by the types of foods we eat, we have seen examples that challenge this idea. We have reviewed the evidence that diets which restrict calories, carbohydrates, and fats are only partially successful for most people. We have examined the idea that excess hunger can cause weight gain in many instances. We have also learned how the intensity of our hunger can be changed by the stress hormone cortisol and by a great variety of medicines. In this chapter, we will explore the theory that caffeine is a drug that can increase hunger and cause obesity.

Increased hunger can explain the rise in food consumption and weight gain in the United States over the last hundred years, weight gain as a side effect of prescription drugs, weight gain from chronic stress, and weight gain from Cushing’s syndrome. Now we will examine how caffeine could affect our body in a way that makes excess hunger occur. We will also explore a likely reason why scientists have overlooked caffeine’s contribution to weight gain and how genetic differences make it difficult to observe the relationship between increased caffeine consumption and increased obesity.

What is Caffeine?

We are constantly surrounded by caffeine in our daily lives. In the doses we consume, caffeine is a stimulant that can make us feel more alert and energetic. Most of us simply assume it is as harmless as any other familiar ingredient in our food. It is not; in fact, caffeine is literally a poison. Caffeine is found in the beans, leaves, and fruits of certain plants. It is harmful even to the plants that produce it, which store it in specialized cells that shield the rest of the plant from its harmful effects. Its purpose is to paralyze and kill insects that eat the plant.²

Make no mistake; caffeine will kill humans as well.³ The amount that we consume in our coffee, tea, and soda is highly diluted. However, two grams of pure caffeine over a short period of time, about the weight of five peas, can result in hospitalization, and twenty grams will kill the average adult.

You are unlikely to get a lethal dose from drinking soda, since you would need to drink forty to fifty 32-ounce cups of it all at once. On the other hand, there are certainly many Americans who get that cumulative dose of caffeine in a week, every week. In fact, there have been deaths⁴ and hospitalizations of people who have taken too many caffeine pills or energy drinks.⁵ In its concentrated form, caffeine is quite lethal to humans. Getting a less than lethal dose of caffeine is still associated with a range of negative effects, and many of these effects cause weight gain.

Caffeine has been implicated in a host of disorders, but not in weight gain in healthy adults. This does not mean caffeine is not partially responsible for weight gain; it just means that we have to look very carefully at the evidence because it is a new theory. First we have to determine whether caffeine can resolve any of the unexplained research on weight gain. Remember the issues associated with weight gain that we have not been able to fully explain. These are the hunger-obesity paradox, why sleep deprivation predicts weight gain, why regular and diet soda consumption predict weight gain, the correlation between stress and weight gain, the decreased use of stored fat in obesity, and the connection to chronic disease. After we examine the role of caffeine in the unresolved issues of weight loss research, we will explore whether caffeine consumption can be a factor in modern weight gain.

Caffeine and Stress

Weight gain has been shown to increase in periods of stress. After an initial stressor has passed, our hunger levels are higher than they would otherwise be. Studies have shown that it is not being overweight that causes stress but being stressed which leads to becoming overweight.⁶ What is unexplained is why Americans should be more stressed than our ancestors who worried about finding enough to eat.

Daily caffeine consumption can partially explain this increased stress. Long-term caffeine use can result in multiple stress hormones becoming elevated, including the hormone cortisol. As explained previously, cortisol is the stress hormone that is also associated with increased hunger. Heightened cortisol production and tissue levels are found in people who are overweight.⁷

Approximately 90% of Americans consume caffeine every day, whether from soda, coffee, tea, energy drinks, or another source. That makes caffeine America’s favorite drug by far. It takes only 200 milligrams (mg) of coffee to measurably increase anxiety levels.⁸ More than half of adults in America are consuming more than 300 mg every day. That is enough to cause muscle twitching, irregular heartbeat, flushing of the face, nervousness, what we commonly think of as caffeine jitters, increased cortisol production, and increased inflammation. Caffeine is socially acceptable as a drug, so we have stopped thinking about its consequences.⁹ After all, how can caffeine be so bad if we are allowing five-year-olds to drink it in soda? However, this reasoning is faulty. It was not too long ago that we placed asbestos in building insulation and lead in paint because we were unaware of the consequences.

There are four caffeine-related psychiatric disorders in the Diagnostic and Statistical Manual of Mental Disorders, and there have been many cases of anxiety disorders that have been successfully treated simply through caffeine abstention.¹⁰ People who have drunk too much caffeine have been mistakenly admitted to psychiatric hospitals for treatment of anxiety disorders.¹¹ Clearly, the effect long-term caffeine use has on our bodies can be profound.¹²

Caffeine and the Hunger-Obesity Paradox

Another characteristic of weight gain we need to explain is the hunger-obesity paradox. People who are obese tend to experience higher levels of hunger than do those who are thin. Since people who are overweight have eaten more than those who are thin have eaten, they should not be hungrier. This suggests that whatever is causing people to be overweight is causing them to be hungrier.

As we have already discussed, caffeine consumption, especially chronic caffeine consumption, raises levels of the stress hormone cortisol. While we do not always think of stressful situations as causing us to eat more, this is because the initial stressor also releases adrenaline. The adrenaline keeps us from being hungry, but it wears off much faster than the cortisol, so later we eat more. Higher production of the hormone cortisol causes raised hunger, even when we have eaten enough.

The hunger-obesity paradox is only a paradox when we think of weight gain as having come about because we have consciously chosen to eat too much food. However, what if caffeine or something else disrupts hormone regulation and causes excessive hunger? If this is the case, then hunger is responsible for our weight gain, meaning hunger and obesity change from paradox to cause and effect.

Caffeine and Sleep Deprivation

Another unexplained predictor of weight gain is sleep deprivation. Chronic sleep deprivation is a feature of modern life and has significant consequences. People who sleep five or fewer hours weigh more than those who sleep seven hours or more. People who sleep less also tend to gain more weight over time. They are hungrier and crave more sweets.^13,14

It is possible that sleep deprivation by itself causes these effects, since sleep deprivation causes cortisol levels to spike, but it is also possible that caffeine consumption is causing people to sleep less and have less restful sleep. Caffeine may be a partial explanation for why we are sleeping less in the modern era. Having 200 mg of caffeine in the morning has been shown to measurably interfere with sleep. This is less than the amount of caffeine in a large cup of coffee and is significantly less than the amount of caffeine the average American adult consumes every day.

Just as we usually eat until we are not hungry, we sleep until we are not tired, unless we are awakened prematurely, such as by an alarm clock. While some of us may miss out on sleep during the work week, we make up for it on the weekends. In the same way as eating too much over the long term has a biological cause, sleeping too little over the long term also has a biological cause. In laboratory tests, people who have been given caffeine before going to sleep exhibit the same symptoms as people suffering from insomnia. With almost 90% of Americans now consuming caffeine daily, it is no wonder that more and more of us are having trouble sleeping.

Since caffeine can cause decreased sleep, the idea that caffeine causes weight gain can explain why people who sleep less gain more weight. Caffeine both interferes with sleep and increases hunger, and increased hunger causes weight gain. This is another example of why correlation does not imply causation. The fact that sleep deprivation and weight gain go together does not rule out some third factor, such as caffeine, causing both of them, rather than one causing the other.

However, most of us drink caffeine in the morning to help us function well upon awakening, and there is little evidence that giving up caffeine will enable us to sleep well enough to wake up at sunrise without an alarm clock the way our ancestors did. Caffeine consumption can explain some disruption of sleep, but we are drinking caffeine because we are having difficulty sleeping soundly enough at night to be alert during the day. There are additional factors disrupting our sleep cycle that we will examine in later chapters, and it is likely that we are drinking caffeine in part to cope with them.

Caffeine and Soda Consumption

We now return to what was a rather startling study discussed previously. Scientists at the University of Texas discovered in an eight-year study that people who drank diet soda were much more likely to gain weight than those who drank regular soda. The reaction to this study was to try to find a reason that artificial sweeteners would cause weight gain. It was not considered surprising that soda made with sugar would cause weight gain, even though we have seen that sugar in juice does not cause weight gain. What we need to do is see if caffeine can explain why both regular soda and diet soda cause weight gain. As presented earlier, here are the data showing the percentages of the normal weight study participants who became overweight or obese, according to their soda consumption.¹⁵

By performing statistical analysis on the results, we can see that drinking diet soda was about 36% more likely to be associated with weight gain than was drinking regular soda, among the subjects in the experiment. That is an extremely interesting number. The diet version of the best selling soda in the United States, whose name will not be mentioned, has 30% more caffeine than its regular version. This degree of difference is only for the most popular soda. The amount varies depending on brand and flavor. If we assume the subjects drank the leading brand of soda, and that caffeine consumption and weight gain have a linear (proportional) relationship, the degree of caffeine difference between regular and diet sodas could explain about 83% of the increased probability of weight gain among diet soda drinkers. There are several caffeine-free regular sodas whose diet versions are not widely sold, and these may account for the remaining difference.

Caffeine provides a plausible explanation for why both regular and diet sodas cause weight gain, as well as why diet soda causes even more weight gain than regular soda. The idea that caffeine causes weight gain, and soda has been a relatively new way for people to consume caffeine, would explain why the problem of weight gain has become so much worse in recent years. It would also explain the problem of childhood obesity. While children almost never drink coffee or tea, many children and teenagers are now drinking very large quantities of soda, not to mention caffeine laden “energy drinks.”

The Problems with the Caffeine Hypothesis

Caffeine consumption has been associated with increases in blood pressure, insulin resistance,¹⁶ raised blood sugar in diabetics,¹⁷ and small increases in cholesterol. People with diabetes and pre-diabetes, who make up about a quarter of the adult population of the United States, appear to be especially sensitive to caffeine.¹⁸ Nevertheless, there is no evidence that caffeine can make someone diabetic or be responsible for the massive increases in cholesterol and other chronic diseases that we associate with obesity. While caffeine’s ability to reduce insulin sensitivity may result in weight gain in diabetics and pre-diabetics, it is probably not enough by itself to do so in healthy individuals.

Coffee was available even in colonial America. After the Boston Tea Party, drinking coffee became an act of patriotism. Despite this, for over a century after the founding of the United States, obesity was rare. In addition, coffee is a traditional drink in the diet of Middle Eastern desert nomads like the Bedouin,¹⁹ having become available in the Middle East by the fifteenth century.²⁰ However, obesity did not become a problem for the Bedouin or in the rest of the Middle East for another five centuries. Changing caffeine consumption does not seem to correspond to the timeline for the rising prevalence of obesity in either the United States or the Middle East.

The theory that caffeine causes obesity does not fit in with many of the things we have been told about weight gain. How does caffeine intake relate to the consumption of processed food and junk food or a healthful diet? Another feature of our diet must be involved in weight gain, even if caffeine is a contributor. A potential culprit is the declining nutrient content of our food. As we will see in the next chapter, caffeine can cause nutrient depletion. While historically caffeine did not produce weight gain in the presence of a nutritious diet, its ability to cause nutrient depletion could be more harmful to people eating the nutritionally deficient Western diet.

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Citations:

¹ Dominique Patton. "Caffeine drinks may contribute to obesity, suggests small study." Decision News Media SAS. 8/09/2009 http://www.nutraingredients.com/Research/Caffeine-drinks-may-contribute-to-obesity-suggests-small-study.

² Dalya Rosner. "Why Plants Make Caffeine." The Naked Scientists. 4/04/2009 http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn2.htm/.

³ S. Kerrigan and T. Lindsey (October 4, 2005). "Fatal Caffeine Overdose: Two Case Reports" (reprint). Forensic Sci Int. 153 (1): 67–69.

⁴ P. Holmgren, L. Nordén-Pettersson, and J. Ahlner (January 6, 2004). "Caffeine Fatalities—Four Case Reports" (reprint). Forensic Sci Int. 139 (1): 71–73.

⁵ R. M. Mrvos and others (December 1989). "Massive Caffeine Ingestion Resulting in Death." Vet-Hum-Toxicol 31 (6): 571–2.

⁶ Jennifer Warner. "Stress Unlocks Fat Cells, Ups Obesity." WebMD. 4/04/2009 http://www.webmd.com/diet/news/20070702/stress-unlocks-fat-cells-ups-obesity.

⁷ Stephen Cherniske. Caffeine Blues: Wake Up to the Hidden Dangers of America's #1 Drug. Grand Central Publishing, 1998, p. 61.

⁸ "Information about Caffeine Dependence." Johns Hopkins Bayview Medical Center. 4/04/2009 http://www.caffeinedependence.org/caffeine_dependence.html.

⁹ L. T. Benjamin, Jr., A. M. Rogers, and A. Rosenbaum (January 1991). "Coca-Cola, Caffeine, and Mental Deficiency: Harry Hollingworth and the Chattanooga Trial of 1911." J Hist Behav Sci 27 (1): 42–55

¹⁰ S. H. Snyder and Pamela Sklar. “Psychiatric Progress: Behavioral and Molecular Actions of Caffeine: Focus on Adenosine.” J. Psychiat. Res. 1984. 91-106.

¹¹ J. F. Greden. “Anxiety or Caffeinism: A Diagnostic Dilemma.” Amer Journ Psychiatry. 1974. 1089-1092.

¹² M. S. Bruce and M. Lader. "Caffeine Abstention in the Management of Anxiety Disorders." Psychological Medicine. Vol. 19, No. 1. Feb. 1989: 211-214.

¹³ Charlene Laino. "Sleep Deprivation Linked to Weight Gain." Medscape Medical News. 4/04/2009 http://www.medscape.com/viewarticle/533105.

¹⁴ Laurie Barclay and Désirée Lie. "Getting Sufficient Sleep May Help Reduce Weight Gain." Medscape Medical News. 4/04/2009 http://www.medscape.com/viewarticle/495410.

¹⁵ Daniel J. DeNoon. "Drink More Diet Soda, Gain More Weight?" WebMD. 4/04/2009 http://www.webmd.com/diet/news/20050613/drink-more-diet-soda-gain-more-weight.

¹⁶ James D. Lane and others. "Caffeine Impairs Glucose Metabolism in Type 2 Diabetes." Diabetes Care. 8/09/2009 http://care.diabetesjournals.org/content/27/8/2047.full.

¹⁷ Idem.

¹⁸ "Diabetes Sufferers: Beware Of Caffeine." CBS News. 8/09/2009 http://www.cbsnews.com/stories/2008/01/29/health/webmd/main3763964.shtml.

¹⁹ Korina Felkers. "Coffee and hospitality: the Bedouin tradition." Examiner.com. 8/09/2009 http://www.examiner.com/x-14074-Boulder-Coffee-Examiner~y2009m8d3-Coffee-and-hospitality-the-Bedouin-tradition.

²⁰ "Coffee." Wikipedia. 8/09/2009 http://en.wikipedia.org/wiki/Coffee.