By Julianne Bierwirth, RD
Coffee has a chemical complexity that, through the roasting process, creates a broad range of vibrant flavor characteristics. This same molecular diversity is also responsible for a variety of health effects in humans. Caffeine is certainly the most well-studied, but it is far from the only pharmacologically active molecule extracted during a brew. Some of these chemicals are elusive, and their effects poorly understood. Others, after decades of research, have concrete benefits and detriments firmly borne out by data.
In this 8-part blog series, we delve into the myriad truths, half-truths, and indeed, fallacies, related to the impact that coffee has on your health. Is it good for you? Is it bad for you? Is it going to make your teeth brown? Does coffee make you smarter? Read on to find out.
PART 8: METABOLISM
Our nation has seen a growing epidemic of obesity in adults and children over the last thirty years. As a result, food, pharmaceutical, and supplement companies have very profitably marketed all kinds of foods with the promise of boosting metabolism. This idea of increasing metabolism has been inextricably linked with weight management in the public mindset. Coffee and caffeine have become common ingredients in these weight-loss products, but before we discuss their efficacy, it’s worth understanding what metabolism actually is and how it rises or falls in individuals.
What is Metabolism?
Metabolism is the umbrella term used to describe the chemical processes by which the body harvests energy to keep itself alive. It includes catabolism (the breakdown of oxygen and chemicals in food to produce energy) and anabolism (the use of these chemicals to rebuild and maintain the body).
If you hear people talk about metabolism it may seem like an internal thermostat that can be set higher or lower by genetics or age. People will often complain that they suffer a slow metabolism and therefore have trouble losing weight, or that they have a fast metabolism and therefore have trouble gaining muscles mass.
It is true that some people have genetically different thyroid activities, or else glean fewer calories from their food due to gastrointestinal function. Hunger, satiety, and energy expenditure are complicated chemical processes, however the energy equation does not change for anyone. If you take in more calories than you burn, you will gain weight. If you burn more than you take in, you will lose weight.
Caffeine may work on both ends of this equation: increasing the amount of energy you burn and decreasing the amount you eat.
Do people who drink coffee eat fewer calories?
There is some evidence to support this idea. Studies have demonstrated a mild suppression of appetite if caffeine is consumed within four hours of a meal. The cause is unclear, though we can take some guesses. Coffee tends to be a mild gastric irritant - causing some stomach discomfort that may discourage eating. Additionally caffeine tends to aid in the alertness and physical capacity needed for productive work. The result might be that we do not as readily recognize the need to eat because we don’t feel as sluggish.
Do people who drink coffee burn more calories?
Whatever “metabolism boosting” effects coffee has seem to be related to the fact that it makes your body move.
Those who drink coffee every day might notice they engage in more incidental movement under its influence. They may pace, fidget, and tense their muscles more than they otherwise would. These non-exercise moments accumulate significantly throughout the day to increase energy output. Additionally, for those who are exercising regularly, caffeine tends to increases the intensity and duration of exercise by up to 25%. In fact, it is considered by many the athletic world's most potent legal exercise aid.
It is worth noting that many people use caffeine to make up for for lack of sleep. This may be a short term strategy to get through the day, however the increased energy associated with a good night’s sleep will also increase daily energy expenditure or “boost metabolism”. Trading sleep for caffeine is not a good weight management strategy.
One of the most promising health effects of drinking more coffee is the potential for reduction in the risk of Type 2 diabetes, a metabolic disorder in the body’s ability to transport and use blood sugar. A study of over 100,000 men and women who increase their intake of full-caffeine coffee by more than one eight-ounce cup per day over a four-year period found an 11% lower incidence of Type 2 diabetes after another four years, whereas those who decrease their intake by at least one cup showed a 17% increase in diabetes incidence.
This effect might be attributable to weight loss, but might also be related to compounds in coffee that block the toxic accumulation of chemicals contributing to diabetes progression. These cups, by the way, are black or with light milk and sugar, not mocha lattes and caramel cappuccinos.
Diabetic coffee drinkers should know that caffeine is associated with a short-term rise in blood sugar, making diabetes management a greater challenge. The American Diabetes Association still suggests that coffee in moderation is an acceptable part of a healthy diet.
There was a time where drinking coffee was considered to be an unhealthy habit akin to smoking or drinking alcohol. Studies from that era were confounded by the fact that many smokers and alcohol abusers were also consuming the highest amounts of coffee, linking their health outcomes with their coffee consumption. Modern science along with a change in coffee drinking culture has done a better job of disentangling the results of these different habits. It it seeming more and more likely that thoughtful coffee consumption may result in a life-long boon to health.
American Diabetes Association. (2017) What can I drink? http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/making-healthy-food-choices/what-can-i-drink.html
Astrup, A., et. Al. (1990) Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers. The American Journal of Clinical Nutrition, 51(5): 759-67.
Bhupathiraju, S.N, et. Al. (2013) Changes in coffee intake and subsequent risk of type 2 diabetes: three large cohorts of US men and women. Diabetologia. https://cdn1.sph.harvard.edu/wp-content/uploads/sites/21/2014/04/Changes-in-coffee-intake-and-subsequent-risk-of-type-2-diabetes_-Bhupathira.pdf
Greenberg, J.A., Boozer, C.N., Geliebter, A. (2006) Coffee, diabetes, and weight control. American Journal of Clinical Nutrition, 84(4): 682-93.
Rustenbeck, I., et. Al., (2014) Effect of chronic coffee consumption on weight gain and glycaemia in a mouse model of obesity and type 2 diabetes. Nutrition & Diabetes ,4(6): e123.
Schubert, M.M., et. Al. (2017) Caffeine, coffee, and appetite control: a review. International Journal of Food Science and Nutrition, 68(8): 901-912.
Van Dam, R. (2015) Ask the expert: coffee and health. Harvard School of Public Health. https://www.hsph.harvard.edu/nutritionsource/2015/02/23/ask-the-expert-coffee-and-health-2/
Zeratsky, K.(2017) Does caffeine help with weight loss? Mayo Clinic https://www.mayoclinic.org/healthy-lifestyle/weight-loss/expert-answers/caffeine/faq-20058459