It’s estimated that there are over 2+ million scientific papers published each year, and this firehose only seems to intensify.

Even if you narrow your focus to fitness research, it would take several lifetimes to unravel the hairball of studies on nutrition, training, supplementation, and related fields.

This is why my team and I spend thousands of hours each year dissecting and describing scientific studies in articles, podcasts, and books and using the results to formulate our 100% all-natural sports supplements and inform our coaching services. 

And while the principles of proper eating and exercising are simple and somewhat immutable, reviewing new research can reinforce or reshape how we eat, train, and live for the better. 

Thus, each week, I’m going to share three scientific studies on diet, exercise, supplementation, mindset, and lifestyle that will help you gain muscle and strength, lose fat, perform and feel better, live longer, and get and stay healthier. 

This week, you’ll learn if periodization helps experienced weightlifters progress, how high-protein dieting affects your health, and whether dehydration kiboshes your athletic performance.


If you’ve been lifting weights for 5+ years, you should probably periodize your training.

Source: “Is stronger better? Influence of a strength phase followed by a hypertrophy phase on muscular adaptations in resistance-trained men” published on November 26, 2020 in Research in Sports Medicine.

Once you’ve been training for more than 3 years or so, there aren’t many levers you can pull to get bigger and stronger.

You can be a bit more disciplined about your diet, sleep, and supplement regimen, focus more on giving your full effort in your workouts, or train more, but with each of these, you quickly reach a point of diminishing returns.

One of the few tools you still have at your disposal, though, is to improve your workout programming, specifically by implementing periodization (systematically adjusting training variables such as volume and intensity over time) .

A notable example of this tactic’s power comes from this study conducted by scientists at the University of Campinas.

The researchers matched 26 experienced weightlifters into pairs based on the thickness of their vastus lateralis (outer quad) muscles, then randomly assigned the weightlifters in each pair to one of two groups: a strength+hypertrophy group or a hypertrophy-only group. (Pairing people based on muscle size helped ensure both folks had roughly the same training experience.) 

Both groups did 2 workouts per week for 8 weeks. The weightlifters in the strength+hypertrophy group did 3 weeks of strength-based training followed by 5 weeks of hypertrophy-based training, whereas the hypertrophy-only group only did hypertrophy-based training.

Specifically, the strength-based training consisted of 4 sets of 1-to-3 reps of the squat and leg press with 3 minutes of rest between sets. The hypertrophy-based training consisted of 4 sets of 8-to-12 reps of the same exercises with 1 minute of rest between sets.

The results showed that the hypertrophy-only group performed more volume load (sets × reps × weight) throughout the study than the strength+hypertrophy group (~103,196 pounds vs. ~80,664 pounds for the squat and ~323,327 pounds vs. ~241,031 for the leg press). Despite this, the strength+hypertrophy group gained more muscle and increased their one-rep max strength more than the hypertrophy-only group. 

This table summarizes the results:


So does this mean everyone should focus on getting stronger before getting bigger?

Not necessarily.

Previous research suggests that people who are new to weightlifting can gain muscle and strength regardless of the type of training they do, so there’s no need for newbs to complicate their training with different phases for strength and hypertrophy.

Other research shows, however, that if you’re a more experienced weightlifter (you’ve been properly training for ~3 years or more) and you’re closing in on your genetic potential for muscle gain, using periodization is one of the most effective ways to continue making progress. 

Strangely, this study also found that those who did the least total work (volume) gained the most muscle and strength. This is contrary to most current research, which generally shows that the more advanced you are, the more work you have to do to continue getting bigger and stronger.

(That’s why I recommend beginners following my Bigger Leaner Stronger and Thinner Leaner Stronger programs do fewer weekly sets than more experienced weightlifters following my Beyond Bigger Leaner Stronger program.)

One limitation of this study was that the weightlifters involved were all young, male, and experienced, so we don’t know if the results apply to women or older people.

The researchers also didn’t control the weightlifters’ diets, which means there’s a chance the strength+hypertrophy group saw superior results because they ate more calories and protein than the hypertrophy-only group.

Finally, the style of periodization in this study is just one out of many you could use, so it’s also not worth getting too fixated on the particulars. By my lights, it’s best to view this study as another piece of evidence that some periodization is probably better than none for experienced weightlifters, rather than proof the precise periodization scheme in this study is optimal. 

These caveats aside, the study provides valuable insight into how experienced weightlifters can ensure continued success. And if you’d like a periodized strength training program designed to help experienced weightlifters reach their genetic potential for size and strength, check out my fitness book Beyond Bigger Leaner Stronger.

(Or if you aren’t sure if Beyond Bigger Leaner Stronger is right for you or if another strength training program might be a better fit for your circumstances and goals, then take Legion Strength Training Quiz, and in less than a minute, you’ll know the perfect strength training program for you. Click here to check it out.)

TL;DR: Once you’ve been following a proper strength training program for several years, you should probably start following a periodized plan to continue getting bigger and stronger. 

Find the Perfect Supplements for You in Just 60 Seconds

You don't need supplements to build muscle, lose fat, and get healthy. But the right ones can help. Take this quiz to learn which ones are best for you.

Take the Quiz

High-protein dieting isn’t bad for your kidneys and liver.

Source: “Case Reports on Well-Trained Bodybuilders: Two Years on a High Protein Diet” published on January 1, 2018 in Journal of Exercise Physiology.

“High-protein dieting might help you build muscle, but it’ll destroy your kidneys and liver in the long run.”

Many health gurus still recite this mantra, and it’s often used as an argument in favor of veganism or vegetarianism (which tend to be much lower in protein than omnivorous diets). 

To put this old saw to the proof, scientists at Nova Southeastern University put 5 experienced male bodybuilders on a high-protein diet (at least 1 gram of protein per pound of body weight per day) for 2 years.

During the experiment, the bodybuilders kept a food diary 3 days per week and went to the lab every 6 months to take tests to measure their kidney and liver health and body composition.

At different points throughout the study, 2 bodybuilders had slightly elevated creatinine levels and 4 had marginally high blood urea nitrogen (BUN) levels, but there was no consistent pattern to how these markers fluctuated.

For example, one bodybuilder had high BUN levels at the beginning of the study and after 2 years, but normal levels at the end of the first year. Another had high BUN levels at the beginning only. And yet another had high BUN levels at the end of year 1 and 2 but not at the beginning.

The most likely explanation for these muddled blood results is that other factors were impacting them. For instance, the bodybuilders may have trained shortly before doing their blood tests, which can elevate both of those blood markers. 

Given these results and the findings of other similar studies, it’s reasonable to conclude that long-term high-protein dieting is perfectly safe, provided you’re healthy.

As an aside, none of the bodybuilders built any appreciable muscle during the study. To see no improvement over 2 years is unusual, even in very experienced weightlifters. This is probably a sign they weren’t training or dieting optimally.

One of the best ways to avoid stagnation like this is to entrust a coach to guide you through the process. 

And if you’d like to learn if hiring a coach is the best way for you to achieve your fitness goals, take the Legion Coaching Quiz now.

TL;DR: Following a high-protein diet (1+ grams per pound of body weight per day) isn’t bad for your kidneys or liver. 

Find the Best Diet for You in Just 60 Seconds

How many calories should you eat? What about "macros?" What foods should you eat? Take our 60-second quiz to get science-based answers to these questions and more.

Take the Quiz

Dehydration doesn’t hurt marathon running performance.

Source: “Inverse relationship between percentage body weight change and finishing time in 643 forty-two-kilometre marathon runners” published on December 15, 2010 in British Medical Journal.

Sports drink manufacturers, coaches, and scientists have been railing against the dangers of dehydration for decades. 

This is particularly true in endurance sports, where hydration has become an almost cult-like monomania. 

While this doctrine rings true (and has sold a lot of Gatorade), research shows it’s mostly hogwash. 

One reason to get over our fear of the dehydration bogeyman is that the fastest athletes are often the most dehydrated.

A good example of this comes from a study published in the British Medical Journal that compared the finishing times and dehydration levels of 643 runners after the 2009 Mont Saint-Michel Marathon.

In this study, the researchers weighed the runners at the beginning and end of the race to calculate the percentage of body weight the runners lost or gained during the marathon. While measuring the percentage of body weight loss after a race isn’t a perfect measure of dehydration, it’s a pretty good proxy.

There are two significant findings from this study.

First, despite all the runners receiving the same advice from the marathon’s organizers about how much they should drink during the race, around ~10% of the runners overdrank, which not only doesn’t improve performance but is potentially fatal

This is pertinent because it means that many people are still swayed by the guff disseminated by misinformed fitness influencers and sports drink marketers, who claim that experiencing any amount of dehydration hinders performance and risks your health.

If you’re an athlete of any stripe—weightlifter, jiu jitsu player, endurance athlete, or anything else—stop guzzling liquid because you’re fearful of dehydration. Drink to thirst and no more

Second, the results showed that the runners lost an average of ~3.7 pounds (2.3% body weight) during the race and that there was a nearly perfect inverse correlation between hydration status and running speed. The fastest runners were consistently the most dehydrated. 

Specifically, runners who finished in less than 3 hours (very fast) were about 3% dehydrated, those who finished in 3-to-4 hours were 2.5% dehydrated, and those who took more than 4 hours to finish were 1.8% dehydrated. It’s worth quoting the researcher’s conclusion in full, as it’s a stark refutation of standard hydration dogma:

“These data are not compatible with laboratory-derived data suggesting that [body weight] loss greater than 2% during exercise impairs athletic performance. They match an extensive body of evidence showing that the most successful athletes in marathon and ultra-marathon running and triathlon events are frequently those who lose substantially more than 3–4% [body weight] during competition.”

Of course, some might argue that these athletes would perform even better if they stayed hydrated, but there are two reasons this thinking doesn’t hold water (harhar): 

  1. Top athletes spend hundreds of hours each year testing various hydration and fueling strategies in their training, and many spend thousands of dollars on gear, coaching, supplements, and training plans to slice seconds off their race times. If simply drinking more water boosted their performance, they’d make damn sure to do it on race day. 
  2. Randomized controlled trials (RCTs) have shown mild dehydration doesn’t decrease athletic performance. 

Remember this the next time you hear someone sermonize about the importance of staying hydrated. 

At this point, you may be wondering, “If water is an essential nutrient, dehydration must hurt your performance at some point, right?”

Yes, but it’s much harder to reach this threshold than most people realize. 

Although scientists aren’t sure exactly how dehydrated you have to be before your performance skids, this point probably varies from person to person and is likely higher than 5-to-10% of body weight (at which point you’ll likely be very thirsty and will want to drink anyway). It also likely improves as you get fitter (as evidenced by the fact that faster athletes can tolerate greater levels of dehydration). 

TL;DR: Dehydration doesn’t negatively affect your athletic performance or health. Drink to thirst, and no more. 

+ Scientific References