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Hydroxycut Hardcore Elite

MuscleTech Performance Series
4.2
★ ★ ★ ★ ★
(23499 ratings)
Theanine 100 mg
Caffeine 270 mg
Product Image
Score74
Strong, inexpensive stimulation may suit experienced users seeking acute energy. Caffeine plus yohimbe creates a high-risk profile for jitters, heart effects, anxiety, and sleep disruption.
How scoring works
Quantity:100 Rapid-Release Thermo Cap(s) • (50 servings)
Goals:
Productivity Boost
Weight Loss
Fitness
Metabolism Boost
Mental Focus

Score 74

Strong, inexpensive stimulation may suit experienced users seeking acute energy. Caffeine plus yohimbe creates a high-risk profile for jitters, heart effects, anxiety, and sleep disruption.
How scoring works
$9.99($0.19 per serving)
iHerb
$ 28.97
Amazon
$ 28.97
Nutrition Faktory
$ 9.99
Report prices

Analysis

Caffeine anhydrous at 270 mg provides a strong acute stimulant dose, with 100 mg L-theanine offering partial calming balance. Green coffee, coleus, cocoa, and yohimbe reinforce the thermogenic and performance positioning.

The formula may support alertness and exercise drive, but it does not provide protein, creatine, hydration, or recovery nutrition. L-theanine cannot reliably offset the combined stimulation from caffeine and yohimbe.

Active amounts and low serving cost are practical strengths. The high-caution stimulant profile makes the product unsuitable for many people and particularly poor for sleep, mood, or stress goals.

Who is it for
  • Stimulant-tolerant adults seeking acute energy
  • Experienced thermogenic supplement users
  • People who can avoid other caffeine sources
Best for
  • Short-term alertness
  • Pre-workout stimulation
  • Thermogenic support

Pros

  • Provides a strong caffeine dose
  • Includes 100 mg L-theanine
  • Fully discloses key active amounts
  • Low serving cost

Cons

  • Aggressive stimulant stack
  • Yohimbe standardization is not shown
  • No sustained-release technology
  • Poor fit for sleep or stress support

Warnings

  • Caffeine plus yohimbe may cause rapid heartbeat, higher blood pressure, anxiety, agitation, or insomnia
  • Avoid combining with other stimulants, decongestants, or high caffeine intake
  • People with heart, blood-pressure, kidney, seizure, or anxiety conditions should avoid unsupervised use
  • Do not use late in the day because sleep disruption is likely

Nutrient quality

65 High impact

Caffeine anhydrous and named coffee species are clear, while yohimbe and coleus lack active-marker percentages. Caffeine and green coffee are substantial, while theanine may partly balance stimulation and several other actives are harder to judge.

.

Ingredient transparency

80 Highest impact

Active amounts are stated and no proprietary blend hides a core dose. Missing excipient details and complete use directions leave the supplied label information incomplete.

.

Customer satisfaction

63 Moderate impact

The supplied aggregate satisfaction average provides a broad signal, while the response volume determines how stable it appears. No comment-level evidence is available to assess repeated complaints or confirm intended-use experiences.

.

Value for money

87 Highest impact

Useful active delivery supports favorable serving value. Several stimulant additions broaden intensity without improving suitability for general use.

.
Report analysis

Goals

Productivity Boost
Productivity Boost
Impact
Highest effect
A Goal FitA- Strength of SupportA CoverageC+ Formula Quality
Theanine · 100 mgCaffeine · 270 mg

Caffeine supplies strong acute alertness, and L-theanine may smooth some stimulant tension. Green coffee and cocoa add stimulation, while the broader fat-burning ingredients have less direct productivity value.

The caffeine and theanine amounts are effective and clearly disclosed. Combining high caffeine with yohimbe may increase anxiety, rapid heartbeat, or blood-pressure effects, especially in stimulant-sensitive users or those using other stimulants.

Study evidence
Caffeine Supportive 108 studies
Theanine Supportive 5 studies
Weight Loss
Weight Loss
Impact
Highest effect
B+ Goal FitB+ Strength of SupportB CoverageB Formula Quality
Caffeine · 270 mg

Caffeine anhydrous provides a strong thermogenic dose, while green coffee, coleus, and cocoa add secondary metabolic support. L-theanine may smooth some stimulant effects, but the non-caffeine botanicals have less consistent evidence for body-composition change.

The active amounts are mostly disclosed and concentrated in a clear energy-focused strategy. The combination of 270 mg caffeine and 56.3 mg yohimbe extract may raise heart rate, blood pressure, anxiety, or sleep disruption in stimulant-sensitive users.

Study evidence
Caffeine Disputed 14 studies
Theanine Not classified

No linked studies yet.

Fitness
Fitness
Impact
Highest effect
A- Goal FitA- Strength of SupportB CoverageC Formula Quality
Caffeine · 270 mg

Caffeine provides a strong evidence-based performance dose that can improve alertness and reduce perceived exertion. L-theanine may soften some stimulant tension, while green coffee and cocoa add related stimulant or polyphenol effects.

Combining high caffeine with yohimbe increases the risk of jitters, rapid heartbeat, anxiety, and blood-pressure effects. Stimulant-sensitive users and people with cardiovascular concerns should avoid this aggressive stack.

Study evidence
Caffeine Supportive 255 studies
Metabolism Boost
Metabolism Boost
Impact
High effect
B+ Goal FitB+ Strength of SupportB CoverageC+ Formula Quality
Caffeine · 270 mg

Caffeine provides a direct thermogenic effect, while green coffee and coleus add possible support for fat use. Evidence is strongest for caffeine and less consistent for the added botanicals.

The disclosed stimulant dose is potent, but the formula favors short-term stimulation over foundational metabolic support. The combination of 270 mg caffeine and yohimbe may increase jitters, rapid heartbeat, or blood-pressure effects in stimulant-sensitive users.

Study evidence
Caffeine Disputed 40 studies
Mental Focus
Mental Focus
Impact
High effect
A- Goal FitB- Strength of SupportB- CoverageD+ Formula Quality
Theanine · 100 mgCaffeine · 270 mg

Caffeine and L-theanine can increase alertness while smoothing some stimulant tension, giving the formula a clear focus mechanism. The large caffeine amount and yohimbe make the effect more aggressive than a typical calm-alertness pairing.

Green coffee, cocoa, coleus, and yohimbe broaden stimulation but add uncertain cognitive value. Combining 270 mg caffeine with yohimbe may increase jitteriness, anxiety, heart rate, or blood pressure, especially in stimulant-sensitive users.

Study evidence
Caffeine Supportive 128 studies
Theanine Supportive 19 studies
Cognitive Support
Cognitive Support
Impact
Moderate effect
C+ Goal FitC+ Strength of SupportD CoverageD Formula Quality
Theanine · 100 mg

Caffeine and L-theanine can support alertness and focus, but the formula is primarily a stimulant weight-management product. The caffeine and theanine pairing has useful human evidence, while the remaining extracts add little reliable cognitive support.

L-theanine at 100 mg is meaningful, but 270 mg of caffeine plus yohimbe creates an aggressive stimulant load. Key active amounts are disclosed, although the extracts lack cognitive standardization details. The combination of high caffeine and yohimbe may raise heart rate, blood pressure, anxiety, or sleep disruption in sensitive users.

Study evidence
Theanine Supportive 25 studies

Ingredients

IngredientAmount per serving
Caffeine Anhydrous
270 mg
Green coffee extract (C. canephora robusta, Chlorogenic Acid)
 200 mg
Coleus extract
100 mg
L-Theanine
100 mg
Cocoa extract (Theobroma cacao)
 100 mg
Yohimbe extract
56.3 mg
Adults 18–50
Report overview
Theanine · 100 mg OverallScore88
B+ Active Ingredient Quality & BioavailabilityA+ Dose, Safety & Label TransparencyB+ Value

The formula provides a clearly disclosed L-theanine amount in the preferred range, but it uses a generic form without added purity evidence. Cost efficiency for the active is competitive. The high caffeine amount combined with yohimbe may increase jitteriness, anxiety, heart rate, or blood pressure in stimulant-sensitive users.

View ingredientView products
Caffeine · 270 mg OverallScore87
B Active Ingredient Quality & BioavailabilityA Dose, Safety & Label TransparencyA+ Value
The formula uses purified caffeine anhydrous at a strong, clearly disclosed dose and offers exceptional cost efficiency. Rapid-release capsules provide immediate stimulation but no sustained-release technology to smooth the effect. Combining the high caffeine load with yohimbe may increase jitters, rapid heartbeat, or blood-pressure effects, especially for stimulant-sensitive users.
View ingredientView products
Loading alternative details
84 Performance

L-Theanine & Caffeine

SR Sports Research
<p>Two hundred milligrams of theanine with 100 mg PurCaf green-coffee caffeine provides a clear two-to-one calm-focus balance, giving a clearer or more purpose-specific option than the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. The softgel oil is not necessary for these water-soluble ingredients, and caffeine timing still matters.</p>
87 Performance

L-Theanine 200 mg Double Strength

Swanson
<p>A focused 200 mg Suntheanine serving offers substantial branded theanine for calm attention and relaxation, giving a clearer or more purpose-specific option than the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. It omits caffeine, so users seeking strong immediate energy would need a different approach.</p>
87 Performance

L-Theanine 100 mg

California Gold Nutrition
<p>A clearly disclosed 100 mg AlphaWave L-theanine serving provides branded, focused support for calm attention, giving a clearer or more purpose-specific option than the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. The caffeine-free design favors relaxation and sensitivity but will not reproduce stimulant-driven energy.</p>
87 Budget

Caffeine 200 mg

ALLMAX
<p>A clearly disclosed 200 mg anhydrous caffeine dose provides direct short-term energy and focus at a lower serving cost than the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. It has no theanine to temper stimulation, so sensitive users may experience jitters or sleep disruption.</p>
85 Budget

L-Theanine 200 mg

California Gold Nutrition
<p>A focused 200 mg L-theanine serving supports calm attention without adding stimulant exposure at a lower serving cost than the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. No branded source or purity marker is supplied, and it will not provide the energy effect of caffeine.</p>
81 Budget

Natural Caffeine

BodyTech
<p>A clearly disclosed 200 mg coffee-derived caffeine dose provides simple stimulant support with a named source at a lower serving cost than the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. The formula lacks theanine and may cause jitters or sleep disruption in sensitive users.</p>
85 Value

Double Strength L-Theanine 200 mg

NOW
<p>A 200 mg L-theanine amount with 100 mg inositol provides simple calm-focus support at an equal or lower serving cost compared with the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. Generic theanine offers less purity assurance than a branded form, and the inositol amount adds little.</p>
82 Value

Caffeine 200 mg

Best Naturals
<p>A clearly disclosed 200 mg anhydrous caffeine serving provides inexpensive, predictable stimulation at an equal or lower serving cost compared with the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. It lacks theanine and offers little beyond stimulation, with routine jitter and sleep-disruption concerns.</p>
83 Value

TheanineUP Focused Energy

California Gold Nutrition
<p>An even 100 mg theanine and 100 mg coffee-fruit caffeine pairing supports alert focus, with cocoa and matcha adding mild complementary stimulation with ingredient clarity that helps justify the higher serving cost compared with the original aggressive blend of 270 mg caffeine, yohimbe, green coffee, theanine, cocoa, and coleus. The one-to-one ratio may feel less calming than a two-to-one formula, and caffeine can still disrupt sleep.</p>
Report alternatives

Sources

Published studies used for the product analysis and the top-ranked studies for each ingredient and goal.

  1. Caffeine administration at night during extended wakefulness effectively mitigates performance impairment but not subjective assessments of fatigue and sleepiness.
    Paech GM; Banks S; Pajcin M; Grant C; Johnson K; Kamimori GH; Vedova CB · Pharmacology, biochemistry, and behavior · 2017
    Randomized trial24 participantsEnergy forCaffeine
  2. L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.
    Sarris J; Byrne GJ; Cribb L; Oliver G; Murphy J; Macdonald P; Nazareth S; Karamacoska D; Galea S; Short A; Ee C; Birling Y; Menon R; Ng CH · Journal of psychiatric research · 2020
    Randomized trial46 participantsStress Relief forTheanine
  3. No effects of caffeine on cycling to exhaustion and perceptual responses in non-caffeine-restricted subjects.
    Weippert M; Behrens M; Schlegel M; Schröder T; Tillmann M; Rühe N; Römer R; Mau-Möller A; Bruhn S · Journal of the International Society of Sports Nutrition · 2025
    Randomized trial56 participantsEnergy forCaffeine
  4. Effect of Combined Ingestion of L-Theanine and L-Arginine for Short-Term Psychological Stress in Young Adults: A Randomized Placebo-Controlled Study.
    Furushima D; Sugiyama I; Nomura Y; Unno K; Yamada H · Journal of nutritional science and vitaminology · 2023
    Randomized trial120 participantsStress Relief forTheanine
  5. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features.
    Juliano LM; Griffiths RR · Psychopharmacology · 2005
    Systematic review66 studies pooledEnergy forCaffeine
  6. Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial.
    White DJ; de Klerk S; Woods W; Gondalia S; Noonan C; Scholey AB · Nutrients · 2016
    Randomized trial34 participantsStress Relief forTheanine
  7. Differential cognitive effects of energy drink ingredients: caffeine, taurine, and glucose.
    Giles GE; Mahoney CR; Brunyé TT; Gardony AL; Taylor HA; Kanarek RB · Pharmacology, biochemistry, and behavior · 2013
    Randomized trial48 participantsEnergy forCaffeine
  8. Safety and Efficacy of AlphaWave® L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled Trial.
    Moulin M; Crowley DC; Xiong L; Guthrie N; Lewis ED · Neurology and therapy · 2024
    Randomized trial30 participantsStress Relief Mental Focus Productivity Boost forTheanine
  9. Does Single or Combined Caffeine and Taurine Supplementation Improve Athletic and Cognitive Performance without Affecting Fatigue Level in Elite Boxers? A Double-Blind, Placebo-Controlled Study.
    Ozan M; Buzdagli Y; Eyipinar CD; Baygutalp NK; Yüce N; Oget F; Kan E; Baygutalp F · Nutrients · 2022
    Randomized trial20 participantsEnergy forCaffeine
  10. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial.
    Hidese S; Ogawa S; Ota M; Ishida I; Yasukawa Z; Ozeki M; Kunugi H · Nutrients · 2020
    Randomized trial30 participantsStress Relief Brain Health Cognitive Support forTheanine
  11. Trait Energy and Fatigue Modify the Effects of Caffeine on Mood, Cognitive and Fine-Motor Task Performance: A Post-Hoc Study.
    Fuller DT; Smith ML; Boolani A · Nutrients · 2021
    Randomized trialEnergy forCaffeine
  12. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses.
    Yoto A; Motoki M; Murao S; Yokogoshi H · Journal of physiological anthropology · 2013
    Randomized trial14 participantsStress Relief forTheanine
  13. Effect of Caffeine on Golf Performance and Fatigue during a Competitive Tournament.
    Mumford PW; Tribby AC; Poole CN; Dalbo VJ; Scanlan AT; Moon JR; Roberts MD; Young KC · Medicine and science in sports and exercise · 2016
    Randomized trial12 participantsEnergy forCaffeine
  14. A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave® L-Theanine on Stress in a Healthy Adult Population.
    Evans M; McDonald AC; Xiong L; Crowley DC; Guthrie N · Neurology and therapy · 2021
    Randomized trialStress Relief Brain Health forTheanine
  15. Effects of Caffeine Intake on Cognitive Performance Related to Total Sleep Deprivation and Time on Task: A Randomized Cross-Over Double-Blind Study.
    Quiquempoix M; Sauvet F; Erblang M; Van Beers P; Guillard M; Drogou C; Trignol A; Vergez A; Léger D; Chennaoui M; Gomez-Merino D; Rabat A · Nature and science of sleep · 2022
    Randomized trial24 participantsEnergy forCaffeine
  16. Comparison of the effects of two amino acids, Gamma-aminobutyric acid (GABA) and L-theanine, on sedation, anxiety, and cognition in preoperative surgical patients - A randomized controlled study.
    Deshpande SS; Kurdi M; Baiju A; Athira AS; Sarasamma AG; Gangadharan AK · Journal of anaesthesiology, clinical pharmacology · 2025
    Randomized trial168 participantsStress Relief forTheanine
  17. Caffeine Supplementation and Physical Performance, Muscle Damage and Perception of Fatigue in Soccer Players: A Systematic Review.
    Mielgo-Ayuso J; Calleja-Gonzalez J; Del Coso J; Urdampilleta A; León-Guereño P; Fernández-Lázaro D · Nutrients · 2019
    Systematic review17 participants17 studies pooledEnergy forCaffeine
  18. The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review.
    Williams JL; Everett JM; D'Cunha NM; Sergi D; Georgousopoulou EN; Keegan RJ; McKune AJ; Mellor DD; Anstice N; Naumovski N · Plant foods for human nutrition (Dordrecht, Netherlands) · 2020
    Systematic review9 studies pooledStress Relief forTheanine
  19. Effect of caffeine intake on fat oxidation rate during exercise: is there a dose-response effect?
    Gutiérrez-Hellín J; Aguilar-Navarro M; Ruiz-Moreno C; Muñoz A; Varillas-Delgado D; Amaro-Gahete FJ; Del Coso J · European journal of nutrition · 2023
    Randomized trial18 participantsEnergy Metabolism Boost forCaffeine
  20. L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study.
    Ritsner MS; Miodownik C; Ratner Y; Shleifer T; Mar M; Pintov L; Lerner V · The Journal of clinical psychiatry · 2011
    Randomized trial60 participantsStress Relief forTheanine
  21. Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
    Payne ER; Aceves-Martins M; Dubost J; Greyling A; de Roos B · Nutrition reviews · 2025
    Meta-analysis50 studies pooledBrain Health Cognitive Support Mental Focus forTheanine
  22. Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task.
    Foxe JJ; Morie KP; Laud PJ; Rowson MJ; de Bruin EA; Kelly SP · Neuropharmacology · 2012
    Randomized trial27 participantsBrain Health Cognitive Support forTheanine
  23. Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study.
    Baba Y; Inagaki S; Nakagawa S; Kaneko T; Kobayashi M; Takihara T · Journal of medicinal food · 2021
    Randomized trialBrain Health Mental Focus Productivity Boost forTheanine
  24. Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study.
    Dassanayake TL; Wijesundara D; Kahathuduwa CN; Weerasinghe VS · Nutritional neuroscience · 2023
    Randomized trial32 participantsCognitive Support forTheanine
  25. Acute effects of theanine, caffeine and theanine-caffeine combination on attention.
    Kahathuduwa CN; Dassanayake TL; Amarakoon AMT; Weerasinghe VS · Nutritional neuroscience · 2018
    Clinical trial20 participantsCognitive Support Mental Focus forTheanine
  26. Cognitive and mood improvements of caffeine in habitual consumers and habitual non-consumers of caffeine.
    Haskell CF; Kennedy DO; Wesnes KA; Scholey AB · Psychopharmacology · 2005
    Randomized trial48 participantsEnergy forCaffeine
  27. Caffeine-containing energy drink improves physical performance of elite rugby players during a simulated match.
    Del Coso J; Ramírez JA; Muñoz G; Portillo J; Gonzalez-Millán C; Muñoz V; Barbero-Álvarez JC; Muñoz-Guerra J · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme · 2016
    Randomized trial26 participantsEnergy forCaffeine
  28. Effect of caffeine ingestion on cycling performance: a systematic review and meta-analysis.
    Wu J; Xu K; Yin M; Ding X; Wang T; Zhang Q; Wu X; Xiao N · Frontiers in nutrition · 2026
    Meta-analysis226 participants20 studies pooledFitness forCaffeine
  29. Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-Analysis.
    Wang Z; Qiu B; Gao J; Del Coso J · Nutrients · 2023
    Meta-analysis254 participants21 studies pooledFitness forCaffeine
  30. Acute Effects of Caffeine Supplementation on Movement Velocity in Resistance Exercise: A Systematic Review and Meta-analysis.
    Raya-González J; Rendo-Urteaga T; Domínguez R; Castillo D; Rodríguez-Fernández A; Grgic J · Sports medicine (Auckland, N.Z.) · 2021
    Meta-analysis12 studies pooledFitness forCaffeine
  31. Sex Differences in the Ergogenic Response of Acute Caffeine Intake on Muscular Strength, Power and Endurance Performance in Resistance-Trained Individuals: A Randomized Controlled Trial.
    Montalvo-Alonso JJ; Ferragut C; Del Val-Manzano M; Valadés D; Roberts J; Pérez-López A · Nutrients · 2024
    Randomized trial76 participantsFitness forCaffeine
  32. Can I Have My Coffee and Drink It? A Systematic Review and Meta-analysis to Determine Whether Habitual Caffeine Consumption Affects the Ergogenic Effect of Caffeine.
    Carvalho A; Marticorena FM; Grecco BH; Barreto G; Saunders B · Sports medicine (Auckland, N.Z.) · 2022
    Meta-analysis60 studies pooledFitness forCaffeine
  33. Effects of modafinil and caffeine on night-time vigilance of air force crewmembers: A randomized controlled trial.
    Wingelaar-Jagt YQ; Bottenheft C; Riedel WJ; Ramaekers JG · Journal of psychopharmacology (Oxford, England) · 2023
    Randomized trial32 participantsMental Focus forCaffeine
  34. Acute effects of caffeine on attention: a comparison of non-consumers and withdrawn consumers.
    Smith AP; Christopher G; Sutherland D · Journal of psychopharmacology (Oxford, England) · 2013
    Randomized trial70 participantsMental Focus forCaffeine
  35. Performance and alertness effects of caffeine, dextroamphetamine, and modafinil during sleep deprivation.
    Wesensten NJ; Killgore WD; Balkin TJ · Journal of sleep research · 2006
    Randomized trial48 participantsMental Focus forCaffeine
  36. Effects of caffeine on mood and performance: a study of realistic consumption.
    Brice CF; Smith AP · Psychopharmacology · 2003
    Clinical trial24 participantsMental Focus forCaffeine
  37. Effects of caffeine or diphenhydramine on visual vigilance.
    Fine BJ; Kobrick JL; Lieberman HR; Marlowe B; Riley RH; Tharion WJ · Psychopharmacology · 1995
    Randomized trial24 participantsMental Focus forCaffeine
  38. Effect of L-theanine on selective attention in a traffic-related reaction task in sleep-deprived young adults: a double-blind placebo-controlled, crossover study.
    Karunaratne UW; Dassanayake TL · Nutritional neuroscience · 2025
    Randomized trial24 participantsMental Focus forTheanine
  39. A Randomized Study to Examine the Ability of a Caffeine-Based Energy Drink to Impact Energy Expenditure, Fat Oxidation, and Cognitive Performance.
    Krieger J; Schrautemeier A; Hagele A; Gaige C; Mennemeyer O; Tolbert S; Iannotti J; Kerksick C; Noonan C; Mumford P · Nutrients · 2025
    Randomized trial60 participantsMetabolism Boost forCaffeine
  40. Oolong tea increases metabolic rate and fat oxidation in men.
    Rumpler W; Seale J; Clevidence B; Judd J; Wiley E; Yamamoto S; Komatsu T; Sawaki T; Ishikura Y; Hosoda K · The Journal of nutrition · 2001
    Randomized trial12 participantsMetabolism Boost forCaffeine
  41. Comparison of changes in energy expenditure and body temperatures after caffeine consumption.
    Koot P; Deurenberg P · Annals of nutrition & metabolism · 1995
    Randomized trial12 participantsMetabolism Boost forCaffeine
  42. Caffeine Increases Work Done above Critical Power, but Not Anaerobic Work.
    Silveira R; Andrade-Souza VA; Arcoverde L; Tomazini F; Sansonio A; Bishop DJ; Bertuzzi R; Lima-Silva AE · Medicine and science in sports and exercise · 2018
    Randomized trial9 participantsMetabolism Boost forCaffeine
  43. Effects of caffeine on alertness.
    Zwyghuizen-Doorenbos A; Roehrs TA; Lipschutz L; Timms V; Roth T · Psychopharmacology · 1990
    Randomized trial24 participantsProductivity Boost forCaffeine
  44. Effects of Different Sources of Low-Dose Caffeine on Mood/Arousal and Cognitive Performance.
    Irwin C; McCartney D; Grant G; Delang N; Bartrim K; Cox GR; Desbrow B · Perceptual and motor skills · 2023
    Randomized trial22 participantsProductivity Boost forCaffeine
  45. Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training. Sea-Air-Land.
    Lieberman HR; Tharion WJ; Shukitt-Hale B; Speckman KL; Tulley R · Psychopharmacology · 2003
    Randomized trial68 participantsProductivity Boost forCaffeine
  46. A review of caffeine's effects on cognitive, physical and occupational performance.
    McLellan TM; Caldwell JA; Lieberman HR · Neuroscience and biobehavioral reviews · 2017
    Narrative reviewProductivity Boost forCaffeine
  47. Acute caffeine supplementation as a nutrition-based strategy to mitigate sleep-loss-related cognitive and operational performance impairments in military personnel: a systematic review and meta-analysis.
    Wang R; Wang W; Meng L; Hao G; Gu G · Frontiers in nutrition · 2026
    Meta-analysis7 studies pooledProductivity Boost forCaffeine
  48. Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials.
    Gerolymos C; Saddier E; Boyer L; Fond G · Molecular psychiatry · 2026
    Meta-analysis1,168 participants31 studies pooledProductivity Boost forTheanine
  49. Effects of L-theanine on cognition, mood and sleep: evidence from human trials.
    Cotter J; Kilpatrick HE · Frontiers in nutrition · 2026
    Narrative reviewProductivity Boost forTheanine
  50. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together.
    Rogers PJ; Smith JE; Heatherley SV; Pleydell-Pearce CW · Psychopharmacology · 2008
    Randomized trial48 participantsProductivity Boost forTheanine
  51. Changes in caffeine intake and long-term weight change in men and women.
    Lopez-Garcia E; van Dam RM; Rajpathak S; Willett WC; Manson JE; Hu FB · The American journal of clinical nutrition · 2006
    Cohort study58,157 participantsWeight Loss forCaffeine
  52. Does caffeine ingestion before a short-term sprint interval training promote body fat loss?
    Ferreira GA; Felippe LC; Bertuzzi R; Bishop DJ; Ramos IS; De-Oliveira FR; Lima-Silva AE · Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas · 2020
    Randomized trial20 participantsWeight Loss forCaffeine
  53. Eight Weeks of Sprint Interval Training With Adding Caffeine Ingestion Leads to Greater Improvements in Health-Related Physiological Parameters in Obese Male Adults.
    Zhiang J; Song Q · Physiological research · 2026
    Randomized trial30 participantsWeight Loss forCaffeine
  54. Caffeine treatment prevented from weight regain after calorie shifting diet induced weight loss.
    Davoodi SH; Hajimiresmaiel SJ; Ajami M; Mohseni-Bandpei A; Ayatollahi SA; Dowlatshahi K; Javedan G; Pazoki-Toroudi H · Iranian journal of pharmaceutical research : IJPR · 2014
    Non-randomized trial60 participantsWeight Loss forCaffeine
  55. The effects of caffeine intake on weight loss: a systematic review and dos-response meta-analysis of randomized controlled trials.
    Tabrizi R; Saneei P; Lankarani KB; Akbari M; Kolahdooz F; Esmaillzadeh A; Nadi-Ravandi S; Mazoochi M; Asemi Z · Critical reviews in food science and nutrition · 2020
    Meta-analysis606 participants13 studies pooledWeight Loss forCaffeine