For many people, coffee is a fairly powerful weight loss tool, as long as you don’t load it down with cream and sugar.
After all, coffee can be a good appetite suppressant.
But, how strong is this effect?
For that matter, how much of it is connected to coffee at all?
What about the relationship between caffeine and weight loss?
Such an effect wouldn’t come as a surprise because there are significant indications that caffeine may be good for health (3). In fact, many of the health benefits of coffee are connected to the action of caffeine.
However, despite the potential connection between caffeine intake and weight loss, relatively few studies have been conducted. One recent piece of research (Icken et al., 2016) published in the European Journal of Clinical Nutrition attempted to address this topic. The authors were specifically interested in whether the consumption of caffeinated beverages was associated with improved ability to maintain weight loss.
The Study Itself
This research study made us of a cross-sectional design. This method compares patterns across two different populations. In this case, one of the two groups were successful at maintaining weight loss, while the other group was representative of the population as a whole.
This study was based in Germany, so both of the sample groups were also from Germany.
The first of these groups, the one with successful weight loss maintenance, contained 494 members. The sample was obtained through the German Weight Control Registry. In contrast, the second group contained 2,129 participants.
The authors found that members of the weight control group did consume significantly more coffee and caffeinated beverages, on average, than the general population.
However, even though the difference was statistically significant, it was a relatively small difference in terms of actual consumption.
Specifically, the difference was roughly half a cup, on average, between the weight loss maintenance category and the general population.
This effect remained statistically significant even when the authors took other patterns into consideration.
However, in the group that was successfully losing weight, there was no association between the amount consumed per day and weight loss. This means that within this group an increased amount of caffeinated drinks did not result in higher levels of weight loss.
The lack of a pattern there is important, as if caffeine was truly contributing to the differences between the two groups - then you'd expect people who consume more caffeine to lose more weight.
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Strengths and Limitations
There is a lot we don’t know about weight loss maintenance and the German Weight Control Registry is focused on figuring out what it is that makes some people successful at maintaining weight.
This is a pretty major strength.
Realistically, there aren’t many studies out there that provide data specifically on people successfully losing weight or keeping it off. In fact, many people seem to assume that weight loss success is a rare occurrence (4).
So, having this data at hand is powerful, especially as participants have managed to actually maintain weight loss. That data could easily be relevant for examining caffeine and weight loss.
Nevertheless, this particular study still had its limitations.
One limitation was that they considered caffeinated beverages as a single category.
That’s fairly unusual and it makes the data hard to interpret, especially in relation to weight loss and caffeine consumption.
As I mentioned before, many people already feel that coffee contributes to weight loss and there is some research to back that up. But, it’s likely that many other caffeinated drinks won’t.
Take energy drinks as an example.
Those tend to be high in calories and it’s extremely easy to drink too much. In many cases, they may also be higher in caffeine than a cup of coffee.
In theory, people who are successfully losing weight or maintaining weight loss should be drinking more coffee and fewer energy drinks. However, it isn’t possible to tell this from the study at hand.
Additionally, the authors were only considering cups of caffeinated drinks.
So, there was no way of estimating the amount of caffeine consumed between the two groups.
These issues completely obscure the relationship between caffeine and weight loss.
In fact, all the authors have really determined is that people who are successful at maintaining weight loss tend to drink more caffeinated beverages.
But, we don’t know how much caffeine they consume or specifically what they are drinking.
The Cross-Sectional Design and Sample Selection
The observational design of the study was also a limitation.
Now, observational research isn’t a bad thing and it has the power to look at patterns across large groups of people. This isn’t something that we can do with experimental research.
However, observational studies don’t have the ability to test cause and effect.
This makes them great as an early look into a given topic – but they can’t prove anything.
Instead, subsequent experimental research is needed to prove a connection.
Now, cross-sectional studies can be a fairly powerful type of observational study because their design mimics that of an experimental study. Specifically, one group can be thought of as the experimental group and the other as a control.
Often, this can be a way of seeing what specific behaviors contribute to their differences.
But, how effective this is depends on the two groups.
In this case, the study is comparing a group that is successfully maintaining weight loss with a group comprised of the general population.
That isn’t the same as comparing those that lose weight to those that don’t. In fact, the two groups even had the same average BMI (25.7 kg/m2).
Realistically, there is little information on how many people in the population group were successfully losing weight. That makes comparisons difficult.
Additionally, the weight loss maintenance sample group came from the German Weight Control Registry.
This registry is part of an ongoing study into weight loss maintenance (5) and people choose to join this study themselves.
That form of recruitment can easily create bias.
In fact, the authors even noted that the participants in the registry were more frequently female, tended to be older, more educated and employed when compared with the general population.
Those factors may have some influence on weight loss success but they would also affect those who joined the study.
As such, comparing these two groups can provide some insight into weight loss maintenance but it is still a limited tool. Consequently, the outcomes of this research should be considered with caution.
The Connection Between Caffeine and Weight Loss
Without a doubt, the authors of this study were looking into caffeine and weight loss. However, the end result of the study wasn’t promising.
While they did find an effect in terms of cups of caffeinated beverages, that effect was fairly small.
In practical terms, a difference of around half a cup, on average, probably won’t make that much of a difference on weight loss.
At the same time, the very design of this study actually makes it impossible to determine whether weight loss and caffeine consumption are connected.
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