No, caffeine doesn’t have calories. But a cup of coffee with cream and sugar does. (Jorge Silva/Reuters)

It is often assumed that caffeine is not good for you. Many view it as a guilty pleasure, addicting, unnecessary and certainly not pro-health. There are so many questions around caffeine: Does it burn fat? Is it dehydrating? Will it improve my athletic performance? Will it prevent me from sleeping?

It seems important to understand what studies are saying about caffeine, considering most American adults have at least one cup of a caffeinated beverage per day.

Exercise performance

Caffeine has long been associated with improving endurance. How does it work? Caffeine makes it easier for the body to use fat as fuel. Thus your body can use both its glycogen reserves and its fat stores to fuel its efforts. This allows for longer periods of aerobic endurance (cardiovascular exercise such as running, cycling or swimming). In addition, the stimulant properties of caffeine can improve cognitive function, so users show more alertness, faster reaction times and decreased perception of pain.


Caffeine is a known diuretic, meaning it increases the passing of urine, although that does not seem to have a significant effect on overall fluid balance. A study in 2013 with individuals drinking the equivalent of five cups of espresso or seven servings of tea found that caffeine does not alter fluid balance in healthy male subjects, regardless of body composition, water intake or physical activity. Although the long-held assumption that caffeine is dehydrating may not be accurate, that doesn’t mean coffee should replace water. You want to drink enough to make your urine clear.

Weight loss and maintenance

Caffeine’s role in weight loss and maintenance hasn’t been studied much. But one study, published in the European Journal of Clinical Nutrition in April, looks promising: Researchers compared the daily consumption of caffeinated beverages between individuals who had maintained weight loss (greater than 5 percent of total weight lost and maintained for over a year) and individuals in the general population. The weight-loss maintainers reported consuming significantly more caffeine than the other group.

The cause of that connection wasn’t clear, though researchers suggested it might be related to a metabolic effect, an appetite-suppressing effect or a caffeine-related rise in energy expenditure. More research is needed, but according to the study’s authors, “Consumption of caffeinated beverages might support weight loss maintenance.”

Type 2 diabetes

Scientists are suggesting that coffee consumption is linked to a significant decrease in Type 2 diabetes. Much more research needs to be done to clarify the data, but one study found that when coffee consumption was increased on average by 11/2 cups per day, the risk of Type 2 diabetes decreased by 11 percent. Another found that every additional cup per day may decrease diabetes risk by 7 percent .


This is one area where all evidence seems to show we should be cutting back on caffeine. Studies show a correlation between caffeine consumption and impaired sleep, which is no surprise. Because caffeine is a stimulant, it can decrease total hours of sleep as well as quality of sleep. Some of this may vary based on genetics and age, as well as typical caffeine consumption, but it is clear that if you are not sleeping well, your caffeine intake should be investigated.


Many people have wondered whether that pounding afternoon headache was a sign of caffeine withdrawal.

To determine whether something is a “drug of dependence,” brain-mapping technology can be used to see whether it triggers the brain circuit of dependence. Although caffeine has not been shown to trigger that pathway, the American Psychiatric Association updated its diagnoses in 2013 and included caffeine withdrawal as a syndrome.


Yes, it’s true that caffeine has zero calories on its own — same for black coffee and tea. But not all coffee cups are equal, for more reasons than just caffeine. It is crucial to know what is in your beverage that might hinder your efforts to maintain a healthy lifestyle. Many of us add sugar and fat to our beverages, causing the calorie count to rise quickly. Also, because caffeine products are a booming industry, there are pre-made mixes, on-the-go drinks and caffeinated bars that are full of calories and processed ingredients.

The bottom line

Still confused about caffeine? Not sure if you should take that drink? Remember the following:

Start with honesty. Measure how much coffee you are having. A serving is an eight-ounce cup. Most small sizes in coffee shops are 12 ounces. If you are trying to assess whether caffeine is affecting your sleep, exercise performance or weight, it is always essential to know your baseline.

Consider your goal. People want to consume or quit caffeine for a variety of reasons. Get clear on your goals, and understand whether drinking or not drinking will support you in achieving them. If you think caffeine might be unhealthy, define what is “unhealthy” to you. Take a closer look at the specific health concerns that are your priorities.

Take a look at what else is in that cup. If you are adding hundreds of calories of fat and sugar to your beverages, it’s probably time to redesign your drink of choice. Maybe start with halving the amount of sugar and fat, and then adjust as needed. Be in control of your food. If you rely on the barista behind the counter, all bets are off.

If you’re not sleeping well, try to cut back. If you want to sleep better or are concerned about your sleep, decreasing or avoiding caffeine might be just what you need.

Do not go cold turkey. If you do want to cut out caffeine, slowly wean yourself off coffee for a week and then go off all caffeinated beverages for 30 days. Assess how you feel and then decide how much, if any, you want to add back.

Berman is a registered dietitian, a personal trainer and owner of Jae Berman Nutrition.