9 pricked fingers, 15 muffins and a poop sample: What it's like to be in a nutrition study

I volunteered my body to science for two weeks and now I know how my body responds to different foods.

Amanda Capritto
7 min read
three muffins sitting on a wooden table top

I consumed many muffins in the name of clinical research.

Getty Images

The morning of Oct. 17, 2019 started differently than most. I jammed a blood sugar sensor into my own arm after, of course, taking deep breaths and giving myself pep talks for 30 minutes. It only stung a little, but as someone who abhors needles, shoving a filament into my own tricep was a serious undertaking. 

That morning I also filled up a test tube with spit (you'd be surprised at how long that takes and, ugh, dry mouth) and configured a flushable basket to my toilet seat so I could scoop up a sample of my own stool -- I know, yuck. 

I did all of these things -- and many more over the next 11 days -- in the name of science. And I'm going to tell you why you should consider something like it, too. 

Watch this: This pill expands to over 100x its own size

What is a clinical trial?

Clinical research is research that involves people who volunteer to be studied for a certain disease, diet, medication, fitness program, health condition, medical product or any combination of those things. There are two types of clinical research: clinical trials (also called interventional studies) and observational studies. 

Interventional studies, the type of research I participated in that involved jamming the filament into my upper arm, evaluate some sort of change on the participants' health. In my case, the researchers used the data from my blood sugar sensor, along with a lot more data I'll describe below, to study how different foods affect my body. 

The Predict study (and its machine-learning parent company)

Predict is, as of yet and probably for the foreseeable future, the largest nutrition intervention study of its kind, with over 2,200 participants from the UK and all 50 US states. 

The distinction of study type is important, says Dr. Tim Spector, one of the scientists leading Predict and professor of genetic epidemiology at King's College London, because "many nutrition studies shared with the public are typically either small intervention studies of 10-20 people that are not representative or they are larger observational studies that are prone to bias."

It all started with a massive clinical study that Dr. Spector led beginning back in 1993, in which he studied the nutritional responses of more than 14,000 sets of twins -- and found that even identical twins have different responses to the same foods. 

To that end, Dr. Spector and his partners, Jonathan Wolf and George Hadjigeorgiou, founded Zoe, the nutritional science and technology company leading the Predict study. Zoe is building a machine-learning algorithm with the anonymized results from Predict, which will allow the researchers to predict -- the name makes sense now -- nutritional responses for anyone who wants them.


Thousands of participants' results from the Predict study are feeding the Zoe app, which will be able to estimate your food responses based on demographics and questionnaires. The app is currently in beta.

Zoe App

In other words, my data -- and the data from the 2,000-plus other participants -- will be used to create an app in which you could answer a few questions and find out how your body will respond to, say, an apple or a slice of pizza. 

The study's methodology; the fact that participants remain in their usual environments and stick to their usual routines; and the utilization of user-generated data (like the food log) produces "an excellent data set that gives us real insights into how different genders, identical twins and different ethnic groups metabolize food," says Dr. Spector.

What is it like to participate in a clinical trial? 

Every clinical trial is different, but I can offer you a synopsis of my experience with Predict. (Have I mentioned that I stabbed my tricep with a small needle?)

All jokes and phobias aside, participating in this study was not easy. Most of the time, it was not fun. Yes, it began with the blood sugar sensor. But that, as hard as it may be to believe after my dogging on so much, was not even the worst part. 

Here's a quick list of the uncomfortable circumstances I endured in the name of science: 

  • I pricked my fingers three times in one day, on three separate days. 
  • I chugged 8 ounces of a sticky, syrupy solution that contained 75 grams of sugar (that's nearly two regular Cokes!) for what is called an oral glucose tolerance test. Twice. 
  • I used a tiny plastic spoon to scoop my own poop from my own toilet and place it in a test tube. And then shook it around as per the instructions. The spoon had an uncanny resemblance to the kind you get at ice cream parlors when asking for a sample -- I'm sorry for that horrible comparison. 
  • I fasted, ate muffins sent to me as part of the study when I really wanted over-easy eggs and bacon, and fasted some more. 
  • I shifted my exercise schedule and switched hours with another CrossFit coach at my gym to comply with the fasting and physical activity instructions. 
  • I attempted to log every morsel of every food I put in my mouth over the course of 11 days. I succeeded, sans an impromptu wine night on which I'm pretty certain I ate a pound of charcuterie on my own. 

I had to prick my fingers as part of the trial.

Getty Images

The Predict study was hard. It tested my nerves, took up a lot of time (curse the act of food journaling, I should've taken my own advice), and threw off my routine.

But it was so, so worth it -- and I haven't even received my results yet. 

If you actually read all of those bullet points, I'm willing to bet you're thinking something along the lines of, "Nope. Never. Not a chance. I won't give up my eggs and bacon, and no way I'm scooping poop with an ice cream sample spoon." 

But even without my results, the Predict study has already helped me in a handful of ways. During this study, I learned that:

  1. My food-logging skills are dreadful. I do not enjoy weighing food or tracking macros
  2. I'm OK with the above because Predict made me weigh and measure all of my food and I feel like I now have a better idea of portion sizes and nutrient equivalents. 
  3. I snack a lot while I'm cooking -- like, eating seven servings of tortilla chips while waiting for my ground beef to brown for the tacos that, yes, I still ate after the many servings of chips. 
  4. Neither my brain nor body function well during fasting periods and I probably wouldn't thrive on an intermittent fasting protocol. 
  5. Even before getting my actual results, I started to notice, thanks to my food log, how certain foods make me feel both physically and mentally.  

Once I get my results back, I'm sure that the poop-scooping and finger-pricking will prove to be even more worthwhile. I'm eager to see the physiological responses to my diet over those 11 days -- combined with the emotional and physical things I noticed as the study was unfolding, I'll be able to make some pretty grand conclusions about what foods my body does and doesn't like. 

I'm particularly excited to see how my body responds to neon sour gummy worms (simple carbs) versus a banana (also simple carbs, but also micronutrients and some fiber). 

I'd be lying if I said that I didn't hope the results were similar, because I'd really like to say, "My body responds the same way to gummies as it does to apples" just in case anyone ever judges me for the sheer number of gummy worms in my diet. 


I really, really love gummy worms, so I'm hoping that my results tell me they're not as bad for me as I think.

Perry Mastrovito/Getty Images

Why participate in a clinical trial at all? 

You mean, other than the super fun things like puncturing your own skin? Am I beating a dead horse? I know I already said all jokes aside, but I'm for real this time. All jokes aside, clinical trials are the heart of medicine. Without them, science -- and thus healthcare -- would never move forward. 

Clinical research is the reason we have safe medications, devices and procedures. It's the science that determines which drugs are safe as over-the-counter and which ones need a prescription. It's the driver of nutrition and fitness guidelines, such as the daily recommended intake for different vitamins and minerals and the Physical Activity Guidelines for Americans. 

Perhaps most importantly, clinical research is the reason that doctors, surgeons and other health professionals can increasingly keep their patients safe and healthy thanks to new medical innovations. 

But it's not just about the researchers and doctors -- clinical research is about the participants. People take part in clinical studies for many different reasons, such as: 

  • Treatments they've tried so far for their health problem haven't worked
  • There's no treatment for their health condition yet
  • They want to find out about new treatments before they're widely available
  • To help find ways to prevent a disease, such as one that affected their family
  • They want to help future generations live healthier lives
  • To help increase diversity in clinical trial populations
  • Simply to learn more about their own health

This is an example of a nutritional curve, the main thing that the researchers are looking for.


Personally, I decided to take part in the Predict study because I'm a total nerd for nutrition science, and I feel like there's a lack of ways to find out how food truly affects your body. Predict offered me a way to gather important insights about my health and diet in my home environment. 

I also decided to participate because the scientists, businesspeople and tech pros behind Zoe and Predict are creating a first-of-its-kind tool to help people all over the globe get those same insights without committing to a clinical study. 

Dr. Spector articulates it best: "Predict is an ongoing scientific program to understand the dimensions of eating: what to eat, which foods to eat together, when to eat and when to be active around eating. We've been given generic one-size-fits-all advice around all of these dimensions for hundreds of years."

Predict's insights power Zoe to empower individuals to know how to eat for their own body. So the more people who participate in the Predict program and who use the Zoe app, the better the answers will be for everyone."

The best health tech at CES 2020

See all photos
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.