Can Drinking Coffee Regularly Help You Lose Weight?

The health benefits of coffee and the regularity with which we consume this caffeinated drink have long been debated. We seem to be told every few months that coffee is the worst thing for us or a means to a long and healthy life.

Today, however, we are looking into the possible connection of coffee with weight loss. Andrew Carey, Group Leader: Metabolic and Vascular Physiology, Baker Heart and Diabetes Institute, discusses the research in detail below.

As eager as they are to learn about the health benefits of drinking coffee, the headlines aren’t always what they seem.

Researchers from the University of Nottingham in the UK recently published a study in the journal Scientific Reports that suggests that caffeine increases brown fat.

This has caught people’s attention because the activity of brown fat burns energy, which can help with weight loss. The headlines claimed that drinking coffee can help you lose weight and that coffee is perhaps also the “secret to fighting obesity”.

Unfortunately, it’s a little more complicated than that. The researchers found that brown fat stimulated caffeine, but this was mainly in the cells of a laboratory.

In order for a human to reap the benefits seen in cells, we estimate that they would need to drink at least 100 cups of coffee.

Although part of this research has looked at people, the methods used do not support coffee or caffeine as options for losing weight.

What is brown fat?

Brown adipose (fatty) tissue is found deep in the torso and neck. It contains types of fat cells that differ from the “white” fat that we find around our waist.

Brown fat cells adapt to our environment by increasing or decreasing the amount of energy they can burn when “activated” to produce heat and keep us warm.

When people are cold for days or weeks, their brown fat improves energy burning.

We know that caffeine may be able to indirectly accentuate and prolong some of these processes, mimicking the effects of exposure to cold in stimulating brown fat.

Brown fat – and anything that is thought to increase its activity – has generated considerable research interest, in the hope that it will help in the treatment of obesity.

What did the researchers do in this latest study?

The research team first conducted experiments in which cells taken from mice were transformed into fat cells in petri dishes. They added caffeine to some samples, but not others, to see if the caffeine-containing cells acquired more brown fat attributes (we call this “browning”).

The dose of caffeine (one millimolar) was determined based on what would have been the highest concentration that would have browned the cells but not killed them.

The fat cell culture experiment showed that the addition of caffeine “browned” the cells.

The researchers then recruited a group of nine people who drank a cup of instant coffee or water as a control.

Before and after the participants drank the coffee, the researchers measured their brown fat activity by evaluating the temperature of the skin near the neck, under which an important region of brown fat is located.

The skin temperature rose in the shoulder area after drinking coffee, while it did not rise after drinking only water.

How should we interpret the results?

Some people criticize the low number of human participants (nine). We shouldn’t make general recommendations on human behavior or medicine based on small studies like this one, but we can use them to identify new and interesting aspects of how our bodies function – and that’s what these researchers have been trying to do.

But whether the increase in skin temperature after drinking coffee is significant cannot be determined for some important reasons.

First, although the study showed an increase in skin temperature after drinking coffee, the statistical analysis for the human experiment does not include enough data to accurately compare the coffee and water groups, which prevents meaningful conclusions. That is, it does not use appropriate methods that we apply in science to decide whether something has really changed or just happened by accident.

Second, measuring skin temperature isn’t necessarily the most accurate indicator for brown fat in this context. Skin temperature has been validated as a way to measure brown fat after exposure to cold, but not after taking medications that mimic the effects of cold exposure, which is caffeine in the context of this study.

I and other researchers have shown that the effects of these “mimic” drugs produce several effects including increased blood flow to the skin. Where we don’t know if changes in skin temperature are due to brown fat or unrelated factors, relying on this measurement can be problematic.

Despite its limitations, PET (poistron emission tomography) imaging is currently our best option for directly measuring active brown fat.

It is the dose that matters most

The instant coffee used in the study contained 65 mg of caffeine, which is the standard for a regular cup of instant coffee. Brewed coffees vary and could be double that.

Regardless, it’s hard to imagine that this dose could increase the energy burning of brown fat when studies using large doses of more potent “cold-mimicking” drugs (such as ephedrine) cause no increase, or at best in modest cases, the activity of brown fat.

But let’s take a look at the caffeine dose used in the cell experiments. The one millimolar concentration of caffeine is a dose 20 times greater than the 300-600 mg dose of caffeine used by elite athletes as a performance enhancing strategy. And this dose is five to ten times higher than the amount of caffeine you’d get from drinking instant coffee.

Rough calculations therefore suggest that we would need to drink 100 or 200 cups of coffee to activate the “browning” effects of caffeine.

So people should keep drinking and enjoying their coffee. But current evidence suggests that we shouldn’t start thinking of it as a weight loss tool, nor that it has anything significant to do with brown fat in humans. – Andrew Carey

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Blind Peer Review

This research scrutiny is a fair and balanced discussion of the study. The limitations identified by this research check apply in the same way to diabetes, which the study included, but was not covered as much in the headlines.

Coffee contains more than caffeine, and although there is evidence that modest coffee consumption can reduce the risk of diabetes, decaffeinated coffee appears to be as effective as caffeinated coffee. This is consistent with the research control’s point that it would be necessary to drink an implausible number of cups of coffee to produce the effect seen with caffeine in cultured fat cells. – Ian Musgrave

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Search controls interrogate recently published studies and how they are reported in the media. The analysis is performed by one or more academics not involved in the study and reviewed by another to make sure it is accurate.

This article on coffee and weight loss has been republished by The Conversation under a Creative Commons license.