Research Roundup #14: Light vs. Heavy Weightlifting, Breakfast and Weight Loss, and L-Theanine and Stress

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 how lifting light weights compares to lifting heavy weights for muscle gain, whether or not eating breakfast can help you lose weight, and why L-theanine may be an actual “chill pill.” 

Table of Contents

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• You may be able to gain just as much muscle using “light” weights as “heavy” weights.
• Does eating a larger breakfast help you burn more calories throughout the day?
• L-theanine helps anxious people cool their jets.

You may be able to gain just as much muscle using “light” weights as “heavy” weights.

Source: “Changes in Body Composition and Strength after 12 Weeks of High-Intensity Functional training with Two Different Loads in Physically Active Men and Women: A Randomized Controlled Study” published on November 12, 2021 in Sports.

When you first dip your toes into the world of weightlifting, here’s the training advice you’re likely to hear: 

1. If you want to gain strength, lift heavy weights for low reps (such as 85+% of your one-rep max for 5 reps or less).
2. If you want to improve your endurance, lift light weights for high reps (such as 30% of your 1RM for 20-to-30 reps).
3. If you want to gain muscle, you should lift moderately-heavy weights for moderately-high reps (such as 60-to-85% of your 1RM for 6-to-12 reps). 

The reality is that these rules are as pat as they are ubiquitous. 

Over the past few years, studies have been piling up showing that high-, low-, and moderate-rep ranges are all equally effective for gaining muscle. Specifically, you can gain equal amounts of muscle using any rep range from 3-to-35 reps per set, provided you take each set within a few reps of failure.

That said, it’s still not clear if “low-load training” (lifting light weights, generally for high reps) is the equal of higher load training in all respects.

For example, studies show that you can build muscle using moderately-heavy weights even if you don’t take your sets to failure (the point at which you can no longer move a weight despite giving your full effort), but is this true of lighter weights? 

We also know that you can keep building muscle for years using moderately-heavy weights, but with lighter weights? 

Some folks also say that you should use low-load training in a periodized fashion—spending a few months using lighter weights and then switching back to moderate or heavy weights, but is this true?

It’s questions like these that scientists at the National and Kapodistrian University of Athens sought to answer when they randomly split 41 physically active men and women into 3 groups: a low-load group that used 30% of their 1RM, a moderate-load group that used 70% of their 1RM, and a control group that didn’t lift weights.

Both groups followed a 3-day training program for 12 weeks. Each workout consisted of four rounds of the bench press, back squat, bent-over row, deadlift, and shoulder press performed as a circuit in that order with 30 seconds rest between sets and 2.5 minutes between circuits. Strangely, instead of assigning each group a particular rep target per set, they had them do as many reps as they could for 30 seconds. Since the low-load group was using lighter weights, they were able to perform more reps, but this design creates a few issues we’ll address in a moment.

The results showed that over the course of the study, both groups completed approximately the same volume load (sets × reps × weight). Specifically, the low-load group lifted a total of ~43,300 pounds and the moderate-load group lifted a total of ~41,900 pounds.

Both groups gained about the same amount of strength on each exercise, though the moderate-load group got slightly stronger overall.

When it comes to body composition, the low-load group lost considerably more fat (-7 lb. vs. -3.6 lb.), and both groups gained a similar amount of muscle (~2.4 lb. for the low-load group and ~2.7 lb. for the moderate-load group).

That said, they gained muscle at different rates throughout the study. The moderate-load group gained an average of ~2.3 lb. of muscle during the first 6 weeks of the study, but only ~0.4 lb. of muscle during the final 6 weeks. The low-load group gained an average of ~1 lb. of muscle in the first 6 weeks and ~1.4 lb. in the final 6 weeks.

This would seem to torpedo the idea that low-load training “stops working” the longer you do it. That said, the researchers used bioelectrical impedance analysis (BIA) to measure muscle gain, which is fraught with errors, so it’s possible this quirky result was just an artifact of faulty measurement.

And what of the importance (or lack thereof) of training close to failure? 

This study doesn’t provide a clear answer, but indirectly suggests you can make good gains training with lighter weights for high reps even if you don’t take your sets to failure.  

Because both groups were limited to lifting weights for just 30 seconds per set, the low-load group was probably stopping their sets long before they reached failure. Basically, they weren’t “allowed” to do as many reps per set as they probably could have, yet they still gained about as much muscle as the folks using moderately-heavy weights.

This stands to reason, because research shows that forcing your muscles to produce mechanical tension is the most effective way to build muscle, and you can do this using light weights for high reps or heavy weights for low reps. 

In other words, both methods produce tension, but in slightly different ways. If you train with light weights and high reps, each rep produces a relatively small amount of tension, but you make up for this by doing more total reps. If you train with heavier weights and lower reps, each rep produces a lot of tension, but you can only do a handful before you have to end the set. And so long as you’re gradually adding weight and/or reps over time (progressive tension overload), you can build muscle with either approach.

There are a few caveats to consider, though.

First, there is a point where higher rep sets with lighter weights ceases to be effective for muscle building. Take cycling, for example, which is just a high-rep, low-load leg workout. While this is great for building endurance, it’s obviously not as effective for building muscle as squats. This is why researchers consider the upper limit of effective high-rep training to be around ~35-to-40 reps (the weight you’re using needs to be sufficiently heavy that you could only do 35-to-40 reps with it before needing to stop).

Second, the weightlifters in this study performed each workout as a circuit, and it’s possible this may have handicapped the benefits of the moderate-load training. If the participants had been allowed to rest a few minutes between sets during their moderately-heavy workouts instead of just 30 seconds, they may have gained quite a bit more muscle and strength than the group using lighter weights for higher reps. 

Third, as mentioned a moment ago, muscle gain was measured using BIA, which can be fickle and inconsistent. Given the small absolute differences between the groups, it’s not out of the question that much of the difference could be chalked up to the foibles of BIA. 

Fourth, the folks in this study were relatively new to weightlifting, which means they’re still likely enjoying some level of newbie gains. While other studies have shown that more experienced weightlifters can also effectively gain muscle using lower-load training, it’s still not clear if this is as universally effective as moderate loads. 

Finally, even if high-rep, low-load training really is as effective as heavy training, there are several practical reasons for favoring lower-rep, higher-load workouts instead: it’s generally more time-efficient, more fun (you get to use heavier weights), better suited to particular exercises (like deadlifts), and far and away better for gaining strength. 

That isn’t to say low-load training has no place in a well-designed strength training program, but it should be a much lower priority than heavy weightlifting. A good rule of thumb is to do about 80% of your sets in the 4-to-10 rep range and 20% above or below that (which is similar to what I recommend in my programs for men and women, Bigger Leaner Stronger and Thinner Leaner Stronger).

TL;DR: Training with light weights may be as effective at helping you gain muscle as training with heavier weights, even when you train far from failure, but it should still make up a relatively small fraction of your workouts. 

Does eating a larger breakfast help you burn more calories throughout the day?

Source: “Twice as High Diet-Induced Thermogenesis After Breakfast vs Dinner On High-Calorie as Well as Low-Calorie Meals” published in March 1, 2020 in The Journal of Clinical Endocrinology and Metabolism.

Nutrient timing is a favorite hobbyhorse among many diet gurus for the same reason most fad diets are appealing: 

It provides an escape from the uncomfortable reality that you must eat fewer calories than you burn to lose weight. 

For instance, you’ve probably heard that if you don’t eat after 7, or 8, or 9 p.m. (or another arbitrary time in the evening) . . . or if you just confine your eating to one or two meals per day . . . or just skip breakfast . . . or fast for one or two days per week . . . then you don’t need to worry about your calorie intake. 

Or if they’re a less unscrupulous charlatan, maybe they’ll concede that calories matter, but contend that their particular nutrient timing strategy will still help you lose more fat than you would otherwise.   

If you understand the concept of energy balance, though, you know that this is bunk. Studies show your basal metabolic rate (the minimum number of calories your body needs to stay alive, which most people refer to as “your metabolic rate”) barely changes throughout the day, and may even slightly increase during the night.

If your metabolism doesn’t stall during the evening, and calories eaten at night aren’t inherently more fattening than calories eaten earlier in the day, are there any benefits to eating less at night?

Possibly.

Some research suggests that eating more calories earlier in the day may increase the thermic effect of food (TEF)—the number of calories your body burns digesting the food you consume. 

The best example of this comes from a study conducted by scientists at the University of Lubeck, where 16 healthy, non-obese men reported to the lab for two 3-day visits that were separated by at least 2 weeks. 

During one visit (large-breakfast condition), they consumed a large percentage of their daily calories at breakfast (69%), a smaller percentage of their daily calories at lunch (20%), and an even smaller percentage of their daily calories at dinner (11%).

And during the other visit (large-dinner condition), they consumed most of their daily calories at dinner (69%), fewer at lunch (20%), and even fewer at breakfast (11%).

The researchers ensured the participants consumed the same number of calories and the same amount protein, carbs, and fat in each visit. They also measured the participant’s energy expenditure before and after breakfast and dinner on each day of the study, and then averaged the results to see which eating schedule produced the highest TEF over the course of the study. Finally, they measured the participant’s level of hunger and desire for sweets before each meal and several hours after dinner.

The results showed that during the large-breakfast condition, the participants experienced over twice as much TEF as they did during the large-dinner condition, which would equate to around 50-to-100 calories per day. 

During the large-breakfast condition they were also less hungry throughout the day and had fewer cravings for sweets. 

Thus, this study would seem to be vindication of the longstanding idea that you should eat breakfast like a king, lunch like a prince, and dinner like a pauper (and perhaps snack like a knight?).  If you take the results at face value, then front-loading your calories at breakfast would inevitably help you lose weight without any extra work on your part.

Before you rejigger your meal plan, though, it’s worth considering a few caveats.

First, if you’re already eating a large breakfast, then it’s not clear if eating even more calories earlier in the day will have additional benefits. For example, if you’re already eating 800 calories in the morning, it’s uncertain if eating even more than this would keep pushing your TEF higher and higher. 

Second, and most importantly, this study wasn’t a true apples to apples comparison between the TEF of breakfast and dinner. We don’t need to get into the nitty gritty details of the study design, but the long story short is that the researchers reported TEF in terms of a percentage increase from baseline—not total number of calories burned. 

This matters because in the large-breakfast condition, the participants consumed most of their calories after an overnight fast, which means their baseline TEF levels would be near rock bottom. In the large-dinner condition, though, they ate most of their calories having already eaten breakfast and lunch, which means their TEF was probably already elevated (since they’d still be digesting their earlier meals).

Therefore, it’s possible the reason the large-dinner group experienced a smaller relative increase in TEF is because their TEF levels were higher to begin with.

Think of it this way: Imagine you’re driving at 30 miles per hour (mph) then accelerate to 60 mph (increasing your speed by 30 mph). Then, another driver who’s parked nearby accelerates to 60 mph (increasing their speed by 60 mph).

Who’s going faster?

Neither of you—you’re going the same speed, but the other driver experienced a larger percentage increase in their speed than you. 

It’s possible the same thing happened in this study—TEF was already revved up in the large-dinner condition, and thus the percentage increase was smaller than that of the large-breakfast condition.

Here’s what this all means: it’s possible that both groups actually burned the same absolute number of calories from TEF, but the large-breakfast group experienced a larger percentage increase in calorie burning after eating their morning meal.

Long story short: the seeming superiority of eating a big breakfast in this study may have more to do with how calorie burning was measured than some inherent fat-burning benefit of eating more earlier in the day.  

Third, another limitation to this study is that the participants didn’t exercise, so we don’t know if the results would apply to people who exercise regularly. Research shows that exercise may increase TEF regardless of when you eat, and it also has positive effects on appetite, which could have affected the results.

It’s also possible that the reason the large-dinner group experienced less TEF is that they weren’t used to eating such a large dinner. 

Research suggests that following a consistent meal schedule may boost TEF and following an irregular meal schedule may decrease TEF. This means it’s possible that once the people in the large-dinner group became accustomed to eating more of their calories in the evening, they would have experienced just as much TEF as the large-breakfast group.

Finally, there’s one more reason to doubt eating in the morning is better than eating in the evening: intermittent fasting.

This popular strategy usually involves skipping breakfast and eating most of your calories later in the day, and research shows it’s just as effective at promoting weight loss as diets that include breakfast.

In sum, eating more calories in the morning might increase energy expenditure and decrease cravings, but there are many reasons to doubt this is the case, and even if it were true, the benefits would be small.

How much you eat over the long-term is going to have a much larger effect on your body composition than when you eat. But if you’re already in a calorie deficit, eating more calories in the morning may help you burn a few more calories per day and feel less hungry. Given that hunger is subjective by nature, play around with eating more or less calories earlier in the day and see how this impacts your appetite (just don’t expect it to help you lose weight on its own). 

If all of this has you curious about the ins and outs of proper dieting—how many calories, how much of each macronutrient, and which foods you should eat to reach your fitness goals—take the Legion Diet Quiz and in less than a minute, you’ll know exactly what diet is right for you. Click here to check it out.)

TL;DR: Although this study seemed to show that eating a larger breakfast helps you burn more calories throughout the day, there are myriad reasons to doubt the results. Most studies show that when you eat doesn’t affect weight loss whatsoever.

L-theanine helps anxious people cool their jets.

Source: “Anti-stress effect of theanine on students during pharmacy practice: positive correlation among salivary α-amylase activity, trait anxiety and subjective stress” published on September 16, 2013 in Pharmacology Biochemistry and Behavior.

L-theanine is an amino acid found primarily in tea. For decades it flew under the radar as just another ho-hum chemical in tea until some studies showed that it could work synergistically with caffeine to amplify its benefits (increased focus and mental acuity) and mute its downsides (increased blood pressure and anxiety). Since then it’s become more and more common to see L-theanine alongside caffeine in pre-workout supplements (like Pulse), but it still isn’t generally taken on its own.

One of the reasons for this is that there just aren’t many studies on L-theanine as a standalone supplement, which is why it’s worth perusing the few that exist. 

To wit, one study conducted by scientists at the University of Shizuoka investigated how L-theanine affected people’s stress levels. They split 20 fifth-year pharmacy students who were assigned to practices (hospitals or drug stores—which are often stressful places to work) into 2 groups: a group that supplemented with L-theanine and a group that took a placebo.

The L-theanine group took 200 milligrams of L-theanine twice per day, one 100 mg tablet after breakfast and the other after lunch, while the placebo group took inert pills instead. The researchers also told the participants to avoid caffeine and other products that might contain L-theanine, like tea, to avoid confounding the results. 

The participants took the supplements for 1 week before going to their jobs (phase 1) and continued for the following 10 days while on the job (phase 2). During this time, the researchers recorded several biological and subjective measures of stress.

The results showed that supplementing with L-theanine after breakfast prevented any increase in salivary α-amylase (a marker of stress) in the morning, though it had less of an effect after a hard day’s work.

This suggests that L-theanine is effective at curbing anticipatory anxiety (working yourself into a lather over future events), but probably doesn’t help you deal with all forms of stress.

L-theanine also boosted subjective well-being among participants who showed signs of high trait anxiety (participants who the researchers deemed to be more likely to feel anxious during stressful situations based on their answers to a questionnaire), though again it was less effective in individuals who didn’t have high trait anxiety.

In sum, L-theanine didn’t “work” for everyone, but it took the edge off stressful events for people who needed it most.

Supplement companies will continue to pair L-theanine with caffeine in pre-workout supplements because it does a great job “pruning” the effects of caffeine—taking away some of the bad while enhancing the good.

This evidence suggests, however, that L-theanine may reduce anxiety on its own with few to no side effects.

And if you’re interested in a 100% natural L-theanine supplement that also contains five other ingredients that improve mood, sharpen mental focus, boost strength, power, and endurance, and reduce fatigue, try Pulse.

(Or if you aren’t sure if Pulse is right for you or if another supplement might be a better fit for your budget, circumstances, and goals, then take the Legion Supplement Finder Quiz! In less than a minute, it’ll tell you exactly what supplements are right for you. Click here to check it out.)

TL;DR: L-theanine helps you feel less stressed about upcoming events and reduces anxiety in chronic worriers.