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 five 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 sleeping longer makes you mentally and physically sharper, how unilateral exercises benefit athletes, how the OMAD diet affects body composition, and more
Table of Contents
Source: “Extended Sleep Maintains Endurance Performance Better than Normal or Restricted Sleep” published in December 2019 in Medicine & Science in Sports & Exercise.
Sleep is like saving money—it’s boring, we know we should do more of it, and it has a considerable and cumulative positive effect on nearly every aspect of our lives.
This study, conducted by scientists at Deakin University, adds another log to the fire supporting sleep’s primacy.
In this study, nine endurance athletes completed three protocols each: A normal sleep condition, a sleep-restriction condition, and a sleep-extension condition. Each protocol lasted four days, and during each period, the participants completed a cycling time trial every day.
Before the experiment started the researchers measured what a “normal night’s sleep” was for each person for four nights to serve as a baseline, and this worked out to about 7 hours per night.
During the sleep-restriction condition the participants slept 30% less than their normal duration (about 5 hours per night), and during the sleep-extension condition, 30% more (about 8.5 hours per night).
Here’s how this affected their performance:
- When the participants slept a normal amount (~7 hours per night), their performance was about the same across all four time trials.
- When the participants slept more than normal (~8.5 hours per night), their performance increased slightly over the four time trials.
- When the participants slept less than normal (~5 hours per night), their performance decreased significantly over the four time trials, dropping from 57.6 minutes on day 1 to 62 minutes on day 4
When the researchers studied the participants’ mood and mental alertness, they found that during the normal and sleep-restricted conditions, the participants tended to show signs of fatigue, disturbed mood, and decreased vigor and mental acuity. In the sleep-extension condition, however, participants were less fatigued, showed no signs of disturbed mood or decreased vigor, and became more vigilant.
It’s worth highlighting that the “normal” sleep duration in this study was only 7 hours, which, based on the results, was still insufficient to maximize the benefits of sleep. Thus, the main takeaway from this study is that if you’re currently getting by with just 6 or 7 hours of sleep (which is very common), bumping this up to 8 or 9 hours will have substantial mental and physical benefits.
If this seems like a long row to hoe, at least try to boost your sleep duration in the nights leading up to a particularly taxing event (an exam, big game, one-rep max test, etc.).
The Takeaway: Increasing your sleep duration from 7 hours to 8.5 hours per night boosts your mood, endurance, energy levels, and mental acuity, while sleeping 5 hours per night causes these markers to dip.
Source: “Effects of Unilateral vs. Bilateral Resistance Training Interventions on Measures of Strength, Jump, Linear and Change of Direction Speed: A Systematic Review and Meta-Analysis” published on July 3, 2021 in Biology of Sport.
A unilateral exercise is any exercise that trains one side of your body at a time. A bilateral exercise is any exercise that trains both sides of your body simultaneously. For example, the Bulgarian split squat is a unilateral exercise, and the back squat is a bilateral exercise.
Unilateral exercises are often touted as more “functional” and better at improving athleticism by many personal trainers, but is this based on sound science or locker-room logic?
That’s what researchers at Shanghai University of Sport wanted to find out when they performed a meta-analysis on 14 studies that looked at the effect of unilateral and bilateral exercises on unilateral strength, bilateral strength, unilateral jumping height, bilateral jump height, change of direction ability, and sprint speed.
There were only two “statistically significant” findings: Bilateral exercises improved bilateral strength more than unilateral exercises, and unilateral exercises improved unilateral jump height more than bilateral exercises. Basically, the participants got better at whatever they practiced.
That said, the scientists also found that unilateral exercises tended to be better than bilateral exercises for improving unilateral and bilateral jumping, agility, and speed (although not to a statistically significant degree).
If you play a sport that requires power, agility, and speed (any sport, basically), it might be smart to include one or two unilateral exercises in your strength training program. Some of my favorites are the Bulgarian split squat, lunge, and step-up for the lower-body, and the single-arm dumbbell overhead press, pulldown, and machine row.
Keep in mind that the results weren’t statistically significant, but there are two other reasons I recommend including some unilateral exercises in your workout routine: they help identify and correct muscle imbalances, and they often make good accessory exercises to the squat, deadlift, and bench press.
(And if you’d like a program that includes a mix of unilateral and bilateral exercises to help you get stronger, faster, and more powerful and athletic, then check out my programs for men and women, Bigger Leaner Stronger and Thinner Leaner Stronger.)
The Takeaway: Unilateral exercises are slightly better than bilateral exercises at improving unilateral and bilateral jumping, agility, and speed, which means they’re useful for improving sports performance.
Source: “Daily Step Count and All-Cause Mortality: A Dose-Response Meta-Analysis of Prospective Cohort Studies” published on August 21, 2021 in Sports Medicine.
Although many fitness folk turn up their noses at walking as a form of cardio, this study shows it’s one of the best ways to stave off disease and prolong your life.
Researchers from Semnan University of Medical Sciences analyzed the results of 7 studies involving a total of 28,141 participants, 175,370 person-years, and 2,310 deaths and found that rates of all-cause mortality dropped about 12% for every 1,000 steps you take per day.
When the researchers compared the people with the highest and lowest daily step counts, they found that walking 16,000 steps per day was associated with a 66% reduction in all-cause mortality compared to walking 2,700 steps per day.
These results were based on observational studies, so they only show that walking is correlated with better health and longer life, but not the cause.
Withal, previous research shows that walking as little as 20-to-30 minutes per day directly boosts cardiovascular fitness and decreases systolic and diastolic blood pressure, resting heart rate, body fat percentage, BMI, total cholesterol, depression, and aches and pains. Although the results of this review might be correlative, the body of evidence shows walking is one of the most underrated ways to improve your health (especially when combined with a proper diet and strength training program).
If you don’t already, try to find time each day to walk—it’ll keep you healthy, happy, and, well, alive.
The Takeaway: This study found that for every 1,000 steps you walk per day, your rate of dying from all causes drops about 12%. Walk as often as you can, as many places as you can, and as far as you can every day. It does your body good.
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.
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
Source: “Effects of chronic betaine supplementation on performance in professional young soccer players during a competitive season: a double blind, randomized, placebo-controlled trial” published on October 18, 2021 in Journal of the International Society of Sports Nutrition.
Many people take betaine to improve their heart and liver function and digestion, but more and more studies, like this one conducted by scientists at the University of Isfahan, show it to be effective at boosting athletic performance, too.
The researchers split 29 young professional soccer players into 2 groups: A group that supplemented with 2 grams of betaine per day and a placebo group. Both groups took two capsules per day two hours before and one hour after training and ate a standardized diet created by a nutritionist.
In the week leading up to the study, at the midpoint, and at the end of the 14-week trial, the researchers put the participants through 5 days of testing and recorded the following data:
- Day 1: Bodily proportions and body composition, lower-body power, and agility.
- Day 2: Bench and leg press one-rep max.
- Day 3: Sprint and acceleration time.
- Day 4: Repeated sprint ability.
- Day 5: Aerobic capacity (endurance).
The results showed that those who supplemented with betaine improved lower-body power (17.1% vs. 5.5%), bench (7.7% vs. 3.4%) and leg press (4.5% vs. 1.7%) strength, 30-meter sprint time (-5.8% vs. +0.8%), peak power during the sprint test (19.3% vs. 6.8%), and endurance (4.9% vs. 1.4%) significantly more than those who took a placebo.
While there isn’t enough research to put betaine on the varsity team with caffeine, creatine, and beta-alanine, the more it’s studied, the more promising it appears. This is why we included 2.5 grams of betaine per serving of our 100% natural pre-workout drink, Pulse.
(If you aren’t sure that Pulse is the right 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.)
The Takeaway: Supplementing with 2 grams of betaine per day significantly boosts lower-body power, bench and leg press strength, 30-meter sprint time, peak sprinting power, and endurance. This and other research shows it’s worth taking.
. . . and it's yours for free. Take our 60-second quiz and learn exactly how many calories you should eat, what your "macros" should be, what foods are best for you, and more.
Some Nutritionists Charge Hundreds of Dollars for This Diet "Hack" . . .
. . . and it's yours for free. Take our 60-second quiz and learn exactly how many calories you should eat, what your "macros" should be, what foods are best for you, and more.Take the Quiz
Source: “Differential Effects of One Meal per Day in the Evening on Metabolic Health and Physical Performance in Lean Individuals” published on January 11, 2022 in Frontiers in Physiology.
“One Meal a Day” (OMAD) is the latest flavor of intermittent fasting, and proponents claim it helps you lose fat quickly without muscle loss, hunger, or sagging energy and performance.
This study shows that’s half true.
Researchers from Amsterdam University put 11 healthy adults on two different diets for 11 days each. One diet involved eating three meals evenly spaced throughout the day, and the other involved eating one meal per day between 5 p.m. and 7 p.m.
Both diets were designed to help participants maintain their weight (they didn’t put the participants in a calorie deficit or surplus), but the researchers didn’t control how much protein, carbohydrates, and fat each participant consumed (their “macros”).
Before and after each diet, the researchers measured the participants’ body composition, markers of cardiometabolic health, and fitness using a barrage of aerobic, anaerobic, strength, and power tests.
The researchers found that people following the OMAD diet lost more fat (0.1 vs. 0.7 kilograms) and overall weight (0.5 vs. 1.4 kilograms) than people following the normal feeding schedule, but they also lost more muscle (0.3 vs. 0.7 kilograms) and saw a larger rise in LDL (“bad”) cholesterol (2.4 vs. 2.8 millimoles per litre). Physical performance was the same regardless of what feeding schedule people followed.
Diets that restrict when you can eat are double-edged swords.
On the one hand, they provide a simple, flexible, and reliable method for helping you eat less. On the other hand, many people struggle to eat enough protein during their feeding window (especially in just one meal per day), and research shows that eating all of your protein in one or two meals is generally worse for building muscle than spreading it evenly throughout the day.
While people’s athletic performance wasn’t significantly affected by OMAD, this study only lasted 11 days, and it’s possible their workouts would have skidded more if the study was longer. And since OMAD did cause muscle loss, this would almost certainly undermine your gains at some point. Other research also shows that fasting diets tend to hinder muscle growth over time.
The rise in LDL cholesterol is a bit of an anomaly, since most research shows fasting reduces LDL, so it’s probably not worth worrying about unless this finding is replicated in future studies.
All in all, OMAD can help you lose weight by limiting your ability to overeat, but it’s not an ideal way to improve your body composition. Instead, a better approach is to use a meal plan to maintain a calorie deficit and eat sufficient protein, eat at least 2-to-3 meals spread throughout the day, and lift weights.
(And if you’d like help setting up a meal plan for your unique circumstances and goals, then take the Legion Diet Quiz! In less than a minute, you’ll know exactly what diet is best for you. Click here to check it out.)
The Takeaway: Eating one meal per day helped people lose more fat, but it also caused more muscle loss and probably would have decreased their performance over time. It “works,” but there are better ways to lose weight.
+ Scientific References
- Roberts, S. S. H., Teo, W. P., Aisbett, B., & Warmington, S. A. (2019). Extended Sleep Maintains Endurance Performance Better than Normal or Restricted Sleep. Medicine and Science in Sports and Exercise, 51(12), 2516–2523. https://doi.org/10.1249/MSS.0000000000002071
- Liao, K. F., Nassis, G. P., Bishop, C., Yang, W., Bian, C., & Li, Y. M. (2021). Effects of unilateral vs. bilateral resistance training interventions on measures of strength, jump, linear and change of direction speed: a systematic review and meta-analysis. Biology of Sport, 39(3), 485–497. https://doi.org/10.5114/BIOLSPORT.2022.107024
- Jayedi, A., Gohari, A., & Shab-Bidar, S. (2022). Daily Step Count and All-Cause Mortality: A Dose-Response Meta-analysis of Prospective Cohort Studies. Sports Medicine (Auckland, N.Z.), 52(1), 89–99. https://doi.org/10.1007/S40279-021-01536-4
- Yang, J. J., Yu, D., Wen, W., Shu, X. O., Saito, E., Rahman, S., Gupta, P. C., He, J., Tsugane, S., Xiang, Y. B., Gao, Y. T., Koh, W. P., Tamakoshi, A., Irie, F., Sadakane, A., Tsuji, I., Kanemura, S., Matsuo, K., Nagata, C., … Zheng, W. (2019). Tobacco Smoking and Mortality in Asia: A Pooled Meta-analysis. JAMA Network Open, 2(3). https://doi.org/10.1001/JAMANETWORKOPEN.2019.1474
- Gellert, C., Schöttker, B., & Brenner, H. (2012). Smoking and all-cause mortality in older people: systematic review and meta-analysis. Archives of Internal Medicine, 172(11), 837–844. https://doi.org/10.1001/ARCHINTERNMED.2012.1397
- Aune, D., Sen, A., Prasad, M., Norat, T., Janszky, I., Tonstad, S., Romundstad, P., & Vatten, L. J. (2016). BMI and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants. BMJ, 353. https://doi.org/10.1136/BMJ.I2156
- Hanson, S., & Jones, A. (2015). Is there evidence that walking groups have health benefits? A systematic review and meta-analysis. British Journal of Sports Medicine, 49(11), 710–715. https://doi.org/10.1136/BJSPORTS-2014-094157
- Nobari, H., Cholewa, J. M., Castillo-Rodríguez, A., Kargarfard, M., & Pérez-Gómez, J. (2021). Effects of chronic betaine supplementation on performance in professional young soccer players during a competitive season: a double blind, randomized, placebo-controlled trial. Journal of the International Society of Sports Nutrition, 18(1). https://doi.org/10.1186/S12970-021-00464-Y
- Olthof, M. R., Van Vliet, T., Boelsma, E., & Verhoef, P. (2003). Low Dose Betaine Supplementation Leads to Immediate and Long Term Lowering of Plasma Homocysteine in Healthy Men and Women. The Journal of Nutrition, 133(12), 4135–4138. https://doi.org/10.1093/JN/133.12.4135
- Ganguly, P., & Alam, S. F. (2015). Role of homocysteine in the development of cardiovascular disease. Nutrition Journal, 14(1). https://doi.org/10.1186/1475-2891-14-6
- Abdelmalek, M. F., Angulo, P., Jorgensen, R. A., Sylvestre, P. B., & Lindor, K. D. (2001). Betaine, a promising new agent for patients with nonalcoholic steatohepatitis: results of a pilot study. The American Journal of Gastroenterology, 96(9), 2711–2717. https://doi.org/10.1111/J.1572-0241.2001.04129.X
- Kathirvel, E., Morgan, K., Nandgiri, G., Sandoval, B. C., Caudill, M. A., Bottiglieri, T., French, S. W., & Morgan, T. R. (2010). Betaine improves nonalcoholic fatty liver and associated hepatic insulin resistance: a potential mechanism for hepatoprotection by betaine. American Journal of Physiology - Gastrointestinal and Liver Physiology, 299(5), G1068. https://doi.org/10.1152/AJPGI.00249.2010
- Yago, M. R., Frymoyer, A. R., Smelick, G. S., Frassetto, L. A., Budha, N. R., Dresser, M. J., Ware, J. A., & Benet, L. Z. (2013). Gastric Re-acidification with Betaine HCl in Healthy Volunteers with Rabeprazole-Induced Hypochlorhydria. Molecular Pharmaceutics, 10(11), 4032. https://doi.org/10.1021/MP4003738
- Pryor, J. L., Craig, S. A. S., & Swensen, T. (2012). Effect of betaine supplementation on cycling sprint performance. Journal of the International Society of Sports Nutrition, 9(1). https://doi.org/10.1186/1550-2783-9-12
- Hoffman, J. R., Ratamess, N. A., Kang, J., Rashti, S. L., & Faigenbaum, A. D. (2009). Effect of betaine supplementation on power performance and fatigue. Journal of the International Society of Sports Nutrition, 6. https://doi.org/10.1186/1550-2783-6-7
- Lee, E. C., Maresh, C. M., Kraemer, W. J., Yamamoto, L. M., Hatfield, D. L., Bailey, B. L., Armstrong, L. E., Volek, J. S., McDermott, B. P., & Craig, S. A. S. (2010). Ergogenic effects of betaine supplementation on strength and power performance. Journal of the International Society of Sports Nutrition, 7. https://doi.org/10.1186/1550-2783-7-27
- Trepanowski, J. F., Farney, T. M., McCarthy, C. G., Schilling, B. K., Craig, S. A., & Bloomer, R. J. (2011). The effects of chronic betaine supplementation on exercise performance, skeletal muscle oxygen saturation and associated biochemical parameters in resistance trained men. Journal of Strength and Conditioning Research, 25(12), 3461–3471. https://doi.org/10.1519/JSC.0B013E318217D48D
- Meessen, E. C. E., Andresen, H., van Barneveld, T., van Riel, A., Johansen, E. I., Kolnes, A. J., Kemper, E. M., Olde Damink, S. W. M., Schaap, F. G., Romijn, J. A., Jensen, J., & Soeters, M. R. (2022). Differential Effects of One Meal per Day in the Evening on Metabolic Health and Physical Performance in Lean Individuals. Frontiers in Physiology, 12, 2495. https://doi.org/10.3389/FPHYS.2021.771944/BIBTEX
- Moro, T., Tinsley, G., Pacelli, F. Q., Marcolin, G., Bianco, A., & Paoli, A. (2021). Twelve Months of Time-restricted Eating and Resistance Training Improves Inflammatory Markers and Cardiometabolic Risk Factors. Medicine and Science in Sports and Exercise, 53(12), 2577–2585. https://doi.org/10.1249/MSS.0000000000002738
- Tinsley, G. M., Moore, M. L., Graybeal, A. J., Paoli, A., Kim, Y., Gonzales, J. U., Harry, J. R., Vandusseldorp, T. A., Kennedy, D. N., & Cruz, M. R. (2019). Time-restricted feeding plus resistance training in active females: a randomized trial. The American Journal of Clinical Nutrition, 110(3), 628–640. https://doi.org/10.1093/AJCN/NQZ126
- Taber, C. B., Vigotsky, A., Nuckols, G., & Haun, C. T. (2019). Exercise-Induced Myofibrillar Hypertrophy is a Contributory Cause of Gains in Muscle Strength. Sports Medicine (Auckland, N.Z.), 49(7), 993–997. https://doi.org/10.1007/S40279-019-01107-8
- Meng, H., Zhu, L., Kord-Varkaneh, H., O Santos, H., Tinsley, G. M., & Fu, P. (2020). Effects of intermittent fasting and energy-restricted diets on lipid profile: A systematic review and meta-analysis. Nutrition (Burbank, Los Angeles County, Calif.), 77. https://doi.org/10.1016/J.NUT.2020.110801