What is a Meta-Analysis and How Can it help You with Fitness?

What a meta-analysis is and how you can use the results from one to help you find the path to reach your fitness goals.

If you do a google search on a topic like dieting or weight loss, you'll come up with all sorts of articles that claim you should do the opposite of one another. It feels really confusing and somewhat overwhelming.

Other people have felt the same way we do, and they set out to answer questions like this by using research and scientific processes. 

A meta-analysis is a type of scientific study that works with the existing research on a topic. The results of different studies are pooled to try and find an average.

Let's break down some of this science for you so you can find out more about how you can chart a path to your goals.

How A Meta-Analysis is Carried Out

There are four steps in carrying out a meta-analysis:

  1. A literature search
  2. Inclusion and exclusion of studies that fit criteria
  3. Quality assessment of studies included in the meta
  4. Statistical analysis of studies

Literature Search

This part of the process involves searching wide across the body of research to see what kinds of studies exist.

The search is performed as wide as possible, as to not leave out important work. If an important study was left out, the results of that study might greatly affect the results of the overall analysis.

Inclusion and Exclusion of Studies

In this part of the meta-analysis process, the researchers choose which studies to include and exclude from the meta-analysis.

The researchers will typically explain clear reasons why they chose to include and exclude certain studies from the meta. One reason for excluding a study might be a lack of disclosing information about the participants of a study. This information might importantly affect the results of a study.

An example of this can be found in a previous post written here about if when you eat protein around exercising matters.

In the meta-analysis I reviewed, some of the studies were excluded from the meta because they did not equate the amount of protein participants ate overall in the entire day. That factor alone can have a significant impact on study results.

Quality Assessment of Included Studies

In this step, the researchers go about deciding whether or not the studies included were carried out using quality measures. 

This part of the process can be pretty subjective, which means the researchers personal bias can come into play. Some choose to combat this by using systematic processes that have been proven to be more objective.

One such tool is the PEDro scale detailed here, a scale that measures the quality of reports of randomised controlled trials indexed on the Physiotherapy Evidence Database.

Statistical Analysis

In the final step of the process, a statistical analysis of the included studies is performed.

The results from each study that made it through the weedout process is grouped, interpreted and presented in an organized fashion.

Two weaknesses of the meta-analysis:

While meta-analysis are extremely valuable and research gold, they are not perfect for two reasons;

  1. Some tests measure different things and can't be compared
  2. Publication bias

One example of tests results that can't be compared are vertical jump.

The way that people perform a vertical jump has not been completely standardized. Some people perform a countermovement first (squat down) others, might choose to start from a paused squat.

These two jumps are actually different things and therefore two different tests. One involves something called a stretch-reflex, while the other does not.

Publication bias is a common problem. It means that statistically, it is more likely to find research showing positive results about an intervention than negative research.

The reasons behind this can be obvious. Some companies perform their own research on whether or not their products are effective. If a product produces positive results, the company will boast about it, if not, they likely won't release that information publically.

Want to Skip Sorting out the Science Yourself?

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How a Meta-Analysis Can Help You

A meta-analysis can point you in the general direction of what might likely work for you.

For example, let's say you wanted to find out how much protein you needed if you were active and played a sport.

You could read this post I wrote that covers everything you might want to know about protein. You could also review  the International Society of Sports Nutrition Position Stand on protein and exercise.

This position stand is actually a systematic review which means it might pool the data from several meta-analysis on a subject and combine that data with expert opinion in order to give insight.

Within the position stand, you would find this about how much protein you should eat as an athlete varies but, generally;

Recommendations regarding the optimal protein intake per serving for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g.

You would be able to now take that information and if you wanted to get specific, go about measuring the results on yourself.

How you Might Measure Results

What I mean by that is, you could get your body fat measured using a DEXA at a place like Advanced Radiology here in Columbia, Missouri, where I do business.

Once you have your baseline results, you might then plan out the two different things you wanted to test, (one protein intake vs another intake) as well as all of the other factors surrounding the test. Ex. your age, overall daily intake or protein, number of overall calories, resistance training program etc.

After you take some time between your two mini experiments on yourself, then you would have a nice little crossover trial performed on yourself that could give you the exact answer as to which of the two intakes is best for you.

Personal training aim's to do this in one way or another when it's done for body composition results.

Hopefully you found this information useful!