What are limitations?

Limitations are frequently discussed in the context of academic research. Limitations are a broad range of things that could influence the quality of the study's data and final conclusion.

Examples of limitations are:

• Missing data
• Factors the researchers didn't consider
• Not enough people in the study to conduct accurate statistical calculations

Lack of diversity can also be a limitation, especially if the study seeks to generalize information to the broader public. The smaller study group needs to mirror the demographics and dynamics of the larger group it seeks to generically represent.

The Issue with Limitations

Limitations can make or break the quality of evidence from a study.

Sometimes it’s what isn’t considered that is most important.

For example, if a study shows that a diet leads to weight loss but does not collect any information about exercise or weight loss medication, that's a problem. In this example study:

• Some people follow a diet only
• Some people follow a diet, but also exercise
• Some people follow a diet, but also take prescription weight loss medication
• Some people follow a diet, exercise, and take medication

But we don't know how many or who did what. We only know that everyone followed the diet. The rest is a big question mark.

The final results of the study report that following X diet leads to weight loss in 85% of the group. While that sounds great, it's meaningless. Because we don't know what percent of the group followed the diet alone. It could have been the 15% that lost no weight at all. Potentially, the diet led to weight gain, but weight loss medication helped to stabilize that, and exercise led to weight loss.

If your head is spinning, you're not alone. Nutrition, fitness, and wellness research is complex because humans aren't simple equations. But researchers know this, and to get answers, they have to design studies to ask the right questions, collect the right information, and recognize the factors that they're not directly studying, but that could have an indirect influence. If they don't identify confounding factors—all the elements that could theoretically cause the effect they're looking for—then they can't answer their research question with confidence.

This is why "checking the research" is never as simple as a quick internet search to see if a study said this or that. It's mostly about reading beyond the summary abstract and looking for what's missing, what wasn't considered, how many people quit before the study was over, and beyond.