Science Spotlight: Alex Leaf


upping your protein game is a prudent choice when overfeeding

- Alex Leaf


Alex is a researcher for, a online encyclopedia on supplementation and nutrition. He is also part of the teaching staff for the Human Nutrition and Functional Medicine program at the University of Western States. Alex's primary focus is on blending science with common sense to help himself and others better understand nutritional research and ways to optimize health through nutrition, fitness, and lifestyle. Check out his articles and scientific publications.

Note: Alex has previously edited articles for SCI-FIT, and is currently working with the team on part 2 of the keto series.


Hello, Alex. Could you give our readers a short introduction to what you do in the world of fitness and nutrition?

Read and write. Oh, and torture young minds trying to earn their master's degree, can’t forget that one.

But seriously, that pretty much sums things up. I’m a researcher for involved primarily in updating the supplement database you all (hopefully) enjoy using, writing and editing articles published in the Examine Research Digest, and writing blog posts. Accordingly, most of my time is spent going down rabbit holes for whatever supplement currently has my attention and trying to communicate that information to you guys in an understandable way. And no, I don’t do all this alone. I have an amazing team at who I rely upon to keep me sane.

My other focus at the moment is teaching. I’m a teaching assistant in the Human Nutrition and Functional Medicine program at the University of Western States. I want to emphasize that I am not a professor or true instructor - just someone who engages with students to make sure they have an awesome learning experience. I currently help teach two courses: Sports Nutrition and Exercise Metabolism (with Tim Sharpe, Chad Macias, Geoff Futch, and Martyn Beaven), and Whole Food Nutrition and Supplementation.

Otherwise, I spend what little free time I have working on blogs that will probably never be finished (I promise to start blogging again at some point, I really do), going on long walks outdoors, lifting heavy things, and eating.

Your first review on overfeeding has just been published in the International Journal of Exercise Science. Tell us about your motivation for writing this piece.

You mean, motivation aside from the fact that I would finally have a piece of peer-reviewed literature with my name on it? That was really the driving point for me. Dr. Antonio broached me with the idea and I went to work finding the relevant data and writing the manuscript with the motivation that I would be a published researcher. I am proud of my publication, especially because no other review on the subject has been conducted that I’m aware of. However, a review article is relatively easy compared to conducting controlled trials or systematic reviews, and I hope to contribute original research in the future. Time will tell.

What is overfeeding and what happens to our body composition when we overfeed?

In our review article, Dr. Antonio and I defined overfeeding simply as eating more calories than required to maintain body weight. Studies determined maintenance requirements either through direct measurement (metabolic ward), indirect measurement (gas exchange plus activity factors or equations), or habitual intake of the study subjects (food logs).

I wish I had as equally simple of an answer for the second part of this question. However, there are countless important pieces of context that influence what happens to body composition during overfeeding, most of which have ZERO research investigating their impact. And frankly, what might seem obvious today could be turned on its head tomorrow.

Let me give you an example.

We reviewed all published literature reporting direct measurements of body composition before and after overfeeding since the beginning of time. Up until 2014, the data consistently showed that overfeeding resulted in weight gain, primarily through increases in body fat. Seems obvious, right? One might argue that overfeeding and weight / fat gain go hand-in-hand - a tautology.

That all changed in 2014 when Dr. Antonio published the first protein overfeeding study in resistance training athletes. Compared to a group of study subjects that didn’t alter their diet, a group that overfed on protein didn’t show any statistically significant differences in body weight, fat mass, or fat-free mass. The overfeeding wasn’t negligible either - these people ate about 800 kcal/d more than the control group. Their protein intake was also significantly higher: 4.4 vs 1.8 g/kg/d.

Follow-up studies by Dr. Antonio replicated these findings, strongly suggesting these initial observations were not an artifact. The second study put people on a structured resistance training program rather than letting the subjects continue their usual training as was done in in the first study, and it reported that eating more calories (+500 kcal/d) from protein (3.4 vs 2.3 g/kg/d) resulted in similar gains of fat-free mass but significant reductions in body fat (no change in normal protein group vs reduction from baseline in high-protein group).

The third study let subjects train on their own again, but used a crossover design to reduce between-group variation from differences that might exist between two separate groups of individuals. Again, eating more calories (+370 kcal/d) from protein (3.3 vs 2.6 g/kg/d) had no significant effect on body weight or composition, although it is notable that 9 of 11 subjects showed a reduction in body fat mass.

So clearly overfeeding does not automatically lead to weight or fat gain - at least in the context of overfeeding on protein and performing resistance training. But we didn’t know this until 2014 with Dr. Antonio’s first study.

Now, to be fair, these studies weren’t without limitations. Humans cannot defy the laws of physics and the extra energy from the protein needs to be accounted for somehow. Diets were not controlled and misreporting of food intake is possible; a systematic review and meta-analysis has suggested that athletes underreport food intake by an average of 20% or about 670 kcal. But this would make Dr. Antonio’s studies more impressive, since underreporting would imply that they overfed to an even greater extent. Assuming dietary reporting was accurate, it is likely that overeating protein resulted in hormonal and metabolic changes that affected nutrient partitioning and energy expenditure, which ultimately allowed for increases in fat-free mass and reductions in fat mass.

This is somewhat of a moot point though. Pragmatically, these findings have value. They show that upping your protein game is a prudent choice when overfeeding. Moreover, resistance-training athletes and fitness enthusiasts are the exact population, in my opinion, with whom overfeeding research should be conducted. If you aren’t active or already lean, then you have no business overeating. However, (recreational) athletes constantly undergo controlled overfeeding periods in an attempt to increase muscle mass - a “bulk”. Therefore, asking how we can maximize muscle gain and minimize fat gain during this period requires further investigation.

But as already mentioned, there is ZERO research investigating most nuances that could affect changes in body composition during overfeeding. We don’t know the effects of manipulating the type or amount of carbohydrate and fat. We also have no data on the effects of macronutrient distribution throughout the day or nutrient timing.

At the moment, the only thing we can say with a relative degree of confidence is that eating more protein when bulking may minimize fat gain, even if it doesn’t help increase lean body mass.

You work for - Could you tell us what the site is about and your role in it? is an independent encyclopedia about supplementation and nutrition that analyzes the full picture of research on any given topic to help you live a healthier life. We are an education company that focuses on providing guides and reviews on nutrition and supplement topics.

What makes stand out from the rest, and a leading reason in my choice to join their team, is that we take an independent and unbiased approach to reporting nutritional science. We are not affiliated with any supplement company or health and wellness company in any way. We don’t sell supplements. We don’t do coaching or consulting. We’re an education company that looks at the research — nothing more, nothing less. One hundred percent of our revenue is generated through our three products: the Research Digest, Supplement-Goals Reference, and the Supplement Stack Guides. was founded in 2011 and I joined the team in 2014 as one of the initial writers of the Research Digest. At the time, I was working for Super Human Radio and had just began my masters program at Bastyr. After graduation, I came aboard as a full-time researcher. Currently, my primary responsibilities at are writing and editing articles for our Research Digest, updating our online supplement database, and writing blog posts.

You have previously worked for Super Human Radio (SHR) as their News Director - Tell us about the show.

I started working for Carl Lanore (the host and founder of SHR) in the beginning of 2014 and was with them until early 2016. I was the person in charge of digging through press releases about health, fitness, and nutrition research to find the most interesting and relevant publications and publishing them on our website for our audience. SHR also served as my first blogging platform, and I would write blogs on a weekly basis about whatever study or topic caught my attention.

As for the show, it is one of the best podcasts out there if you enjoy learning about any and all things related to health. There is no single focus and topics span more subcategories of health, diet, lifestyle, and fitness than any other podcast I have come across. The real selling point, though, is that very little is scripted or planned. Instead, Carl engages in organic conversations as if he had just met the guest in person at a conference.

Another really cool thing about SHR is that you are going to have your beliefs challenged, if for no reason other than that anyone is welcome on the podcast - there is no agenda that Carl pushes and no viewpoint he won’t entertain. After all, open and cordial discussion is how we learn and (hopefully) evolve our viewpoints to be consistent with the best available evidence.

Importantly, the diversity of guests and viewpoints means that you need to approach SHR with some healthy skepticism. Guests are likely to have biases (we all do), and some guests might not be complete experts on the topic of discussion, thus increasing the chances of them spouting misinformation from an authoritative standpoint. Carl will call them out on it when appropriate, but Carl doesn’t know everything (no one does) and can be mislead just as easily as you or me. Still, Carl never claims to be an expert on most topics and ge has a tremendous amount of integrity that is hard to come by. He fully supports having an open mind and using critical thinking skills.

Which projects are you currently working on (research and other works)?

I’m working on a few things at the moment, some of which I can’t tell you about. I will say that one of them is going to be another peer-reviewed publication with Dr. Antonio, while the others are some goodies for 2018.

What I can say is that I am currently in the process of updating’s pages on glycine and collagen and then plan to create pages for resistant starch and exogenous ketones. After that, we’ll see what catches my interest to research next. I also have a backlog of blog posts I need to update or write anew.

On a personal level, I have been working on a blog series about all things protein. The running title at the moment is A practical guide to protein, with the intention of it being a one-stop-shop for any and all questions related to protein. What is it and what does it do in the body? How much should we eat - broken down by health goal and individual-level context? What are the risks of eating high-protein diets? And so forth. Ultimately, I want it to be actionable information, meaning that you can read the blog for educational purposes but also leave with pragmatic recommendations.

I really do want to start blogging again, and my protein series is how I plan to start. I have no idea how often I’ll have new content, but rest assured there are many topics that I want to discuss. So, stay tuned.

What would you say are your best articles, and why?

Hmm… that’s a tough question.

I think that some of my best work are the articles I write for the Research Digest because they require that I not only critically analyze a single study, but also put the study findings into the context of other research and the bigger picture of whatever is being investigated. They also require that I discuss research in a way that can be understood by both the interested health enthusiast and the knowledgeable health expert.

While I can’t link to some of my favorites because the Research Digest is paid content that we rely upon to stay afloat over at, there are a couple of ones that I wrote which have appeared as blog posts. These include how cheese, fatty meat, and carbs compare regarding their effects on cardiovascular disease risk, how dietary carbohydrate influence blood lipids, a pill for people with gluten intolerance, arachidonic acid as a bodybuilding aid, and whether gluten makes you fat.

On a professional level, I’m incredibly proud of my review article on overfeeding because it is the first peer-reviewed manuscript I authored and required me to completely alter my writing style and the way in which I think about research.

There are also several articles from my time at SHR that I am proud of.

  • One of my more popular articles, Why you may reconsider buttering your potato (2015), was the result of my exploration down the Randle Cycle rabbit hole. If you understand that, then you’ll enjoy my article. If you didn’t, then I think my article might give you some serious food for thought on the contemporary notion that “balanced” meals are best.
  • Another personal favorite was Vinegar - glycemia’s best friend (2015), an article that kick-started my pre-meal vinegar shot habit.
  • Finally, I wrote two rebuttal articles that let me explore the land of logical fallacies commonly used to perpetuate misinformation. The first, To peanut or not to peanut? (2015), was a response to the seemingly endless stream of questions I would receive about the healthfulness of everyone’s favorite food - peanuts and their delectable butter. The second, Proteinaholic rebuttal (2016), was a response to a book published by Garth Davis and Howard Jacobson, the latter of whom came on SHR for an interview about the book and served as my reason to write the article.

What do you want to achieve with your work in the future?

My end-goal with everything I’m doing is to simply educate myself and others and help clear some of the confusion that is rampant in nutritional science. I believe that my positions as a researcher for, as part of the UWS faculty, and as a (hopeful) blogger put me in a unique position to accomplish this goal.

I don't have all the answers and I don't pretend to. One of the things I like most about my work is that it let’s me continuously challenge my personal beliefs and evolve my mindset in the face of new evidence. And this is something I hope to help others with as well. I want to promote critical thinking and self-efficacy with my writing and teaching. That is, I want to teach you to fish rather than just give you a fish.

Which research topic do you think needs more attention?

Too many. But if I had to pick one, definitely the effects on body composition of controlled overfeeding in resistance training athletes looking to bulk. This is spurred in part by selfish motives, since the research would be directly applicable to myself, but it’s also spurred by the fact that less than ten studies have been published on this topic that I am aware of. There are many nuances I would love to investigate further.

Do you want to give any shoutouts?

I do. First and foremost, I want to thank both Adel Moussa (SuppVersity) and Sean Casey (Dietetic Advantage and Case Performance) for putting up with me when I was a young Primalkid browsing fitness and nutrition forums. You can probably still find my comments on places like Lyle McDonald’s body recomposition forum. Adel’s patience for my never ending stream of questions was on a whole other level. And Sean… he literally did my diet and training for me for over a year while I recovered from some personal issues and couldn’t muster the mental strength to think through that stuff for myself. I’m proud to call both them both great friends and mentors.

Next, I want to give a shoutout to Carl Lanore. This man gave me the opportunity to get started in this field when he brought me aboard Super Human Radio and is probably the only reason any of you know who I am today. He also provided me with the platform necessary to start my journey into nutritional science and critically analyze some of my deep-held beliefs. Ultimately, he taught me the value of having an open mind.

Finally, I want to thank Sol Orwell and Kamal Patel for giving me the opportunity to be with My skills as a writer and nutrition researcher truly evolved to the next level through them, and I could not be happier with where I am currently. I love the team and environment, and I don’t plan on leaving any time soon (if ever).

Alex’s Research

Peer-reviewed publications

  • The Effects of Overfeeding on Body Composition: The Role of Macronutrient Composition - A Narrative Review (Leaf and Antonio, 2017)

Alex’s Articles

Examine Research Digest Articles

Here are some of the Research Digest articles Alex has written:

SuperHumanRadio Articles

A long list of Alex’s SuperHumanRadio articles can be found here. Below is a selection of some of his articles:

Suppversity Guest Posts

Podcast Appearances

Alex maintains an up-to-date list of podcasts he has appeared on, on his website.


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