Welcome to
Using Scientific Theory to Achieve your Fitness Goals
The Theory of Fitness Approach
Theory of Fitness is all about educating people on how to live healthier through exercise, nutrition and recovery. We do this while sticking to our mantra 'using science based evidence to further our theory of fitness'.
Using Theory of Fitness you you'll have a professional, experienced and knowledgeable personal trainer who will write your programs, explain the rationale and help you reach your goals.
Check out our basic tools to help with your fitness journey or see our personal training options below.
About Lewis Black
Lewis created Theory of Fitness with the belief that fitness should be accessible to everyone and so has set out to achieve the goal of getting as many people to be as fit and healthy as possible.
To achieve this Lewis completed a BSc in Sport and Exercise Science, L3 Extended Diploma in Sport, L3 Diploma in Personal Training, L2 Fitness Instructor, and L2 Spin Qualification among various other qualifications. Using the theory, we help individuals achieve their fitness goals by creating personalized plans that take into account their unique needs and abilities.
![What if scrolling fitness content actually boosts your exercise behaviour?
Research from 2025 shows something fascinating:
People who regularly engage with fitness content online (such as watching, liking, commenting) are more likely to actually exercise more often.
That’s not just inspiration... it’s a real psychological link:
👉 Content increases intrinsic motivation
👉 That increases intentions to exercise
👉 Which translates into actual behaviour
In short:
Your feed isn’t just entertainment - it’s influencing what you do.
So next time someone says social media is a waste of time…
Tell them it might be part of the reason they started training in the first place.
Save this if you’ve ever been inspired to train by a post.
Follow for more evidence-based fitness insights.
Xiao, X. Huang, D. Li, G. (2025) The impact of fitness social media use on exercise behaviour: the chained mediating role of intrinsic motivation and exercise intention. Frontiers in Psychology. [Online] 16 (1) DOI: 10.3389/fpsyg.2025.1635912
#Fitness #Exercise #Health #PersonalTraining #Explore](https://scontent-sea5-1.cdninstagram.com/v/t51.82787-15/626550840_17994694841871826_3004713139769184067_n.webp?stp=dst-jpg_e35_tt6&_nc_cat=102&ccb=7-5&_nc_sid=18de74&efg=eyJlZmdfdGFnIjoiRkVFRC5iZXN0X2ltYWdlX3VybGdlbi5DMyJ9&_nc_ohc=KFU3HzmC3sgQ7kNvwGZKxz4&_nc_oc=AdkauqTxytLkZ9nzZZYcrGjA6oKivTCSmrN1fYjK9nW1JSI5WLF14gxMiP1kdr1Bl-E&_nc_zt=23&_nc_ht=scontent-sea5-1.cdninstagram.com&edm=ANo9K5cEAAAA&_nc_gid=5vby89nZqFAMJo5xIRFgPQ&oh=00_AfuqqQ2vhOk3lMuno8TkgEm5I2Gd_yIIAcLv-61qVSAU5A&oe=6987EDA8)
![Rapid fat loss can work... but it often comes with trade-offs that people rarely talk about.
Losing weight quickly can reduce fat, but the speed of the change can also affect your body in ways people don’t expect or really think about, from changes in hormones and hunger signals, to potential loss of muscle mass (in the absence of exercise) and effects on performance and recovery.
One peer-reviewed study on the effects of rapid weight loss showed that while short-term reductions in body weight can reduce fat mass, the long-term effects on body composition and the mechanisms behind them aren’t fully understood.
And worse still, rapid approaches tend to come with challenges that slower, more gradual changes might avoid.
Rapid loss is often linked with:
• Changes in metabolic and hormonal signals
• Harder time maintaining energy levels
• A less sustainable approach over time
• Potential loss of lean mass if nutrition/training aren’t dialled in
Sustainable progress is about fat loss with minimal downsides, not just hitting numbers fast.
That’s the balance most people miss.
Save this if you’re trying to lose fat the right way.
Follow for more evidence-based training and nutrition breakdowns.
Kadowaki, R. Aoyama, T. Hada, Y. Aihara, M. Sawada, M. Sekine, R. Itoh, H. Kadowaki, T. Kubota, N. Yamauchi, T. (2024) Effects of rapid weight loss on the body composition and pathophysiological mechanisms involved in obesity. Endocrine Journal. [Online] 72 (3). DOI: 10.1507/endocrj.EJ24-0315
#FatLoss #PersonalTraining #Northampton #Health #fitness](https://scontent-sea5-1.cdninstagram.com/v/t51.82787-15/622023843_17993964146871826_1884944220405615738_n.webp?stp=dst-jpg_e35_tt6&_nc_cat=103&ccb=7-5&_nc_sid=18de74&efg=eyJlZmdfdGFnIjoiRkVFRC5iZXN0X2ltYWdlX3VybGdlbi5DMyJ9&_nc_ohc=fyeFyEOf9agQ7kNvwE55-sV&_nc_oc=Adk6Hfe9oPS63CoNDv0dAo08dsNRwr_IPi0pHXuoyeNfb858cYMInYgs8d4UbxbEo9A&_nc_zt=23&_nc_ht=scontent-sea5-1.cdninstagram.com&edm=ANo9K5cEAAAA&_nc_gid=5vby89nZqFAMJo5xIRFgPQ&oh=00_AfvAVny-tNT00vY2cmWS3m1X_yiMMrjNHc7nrrWFTn1Bgw&oe=6987EBA2)
![TRE (time-restricted eating) + lifting: what the science says (2024 meta-analysis)
A 2024 systematic review/meta-analysis looked at time-restricted eating combined with resistance training vs normal eating + resistance training.
What happened?
More fat loss / weight loss on average
Insulin + cholesterol improved
Muscle mass + strength were NOT reduced compared with normal eating *when training was in place*
What this means in real life:
If you’re lifting properly, TRE can be a structure tool for fat loss without automatically costing you muscle... but it’s not magic. It likely helps because many people naturally eat fewer calories.
How I apply it with my clients:
Pick an 8–10 hour eating window you can stick to
Lift 2–4x/week, progress basics
Prioritise protein + total weekly intake
If performance tanks, expand the window / adjust carbs around sessions
It is not for everyone:
History of disordered eating, pregnancy, or if you’re managing medical conditions/meds then get clinical guidance. Want me to set this up around your training + schedule? Contact me and I’ll tell you exactly how I’d run it for your goal.
Ho Y. Hou, X. Sun, F. Wong, S.H.S. Zhang, X. (2024) Synergistic Effects of Time-Restricted Feeding and Resistance Training on Body Composition and Metaboilc Health: A Systematic Review and Meta-Analysis. Nutrients. [Online] 16 (18). DOI: 10.3390/nu16183066
#health #fitness #diet #fatloss #weightloss](https://scontent-sea5-1.cdninstagram.com/v/t51.82787-15/618676985_17993227994871826_8153335604890434945_n.webp?stp=dst-jpg_e35_tt6&_nc_cat=111&ccb=7-5&_nc_sid=18de74&efg=eyJlZmdfdGFnIjoiRkVFRC5iZXN0X2ltYWdlX3VybGdlbi5DMyJ9&_nc_ohc=FS75zq82Cp8Q7kNvwG_oHH5&_nc_oc=AdkyrzogLVt7hPIfVzCMJls2gRSWeRVxSfhJXfLLQA0LNKQYd-oQtVfU4yQ_ZkAZAC0&_nc_zt=23&_nc_ht=scontent-sea5-1.cdninstagram.com&edm=ANo9K5cEAAAA&_nc_gid=5vby89nZqFAMJo5xIRFgPQ&oh=00_AftF_-RI_ZM9RRgBwwnIqj5iyqNivdmfntLEMAjuHetjYA&oe=6987DB11)
![Want to know how Orange Juice might reduce depression?
A new small trial found that young adults with depression who drank flavonoid-rich orange juice every day for 8 weeks saw greater improvements in depressive symptoms compared with those drinking a low-flavonoid orange drink. Changes in blood markers and gut bacteria were also seen, hinting at possible ways the juice might influence the gut-brain connection.
This doesn’t mean orange juice treats depression, but it’s an interesting piece of evidence that diet and plant compounds like flavonoids might play a role in mental well-being. More research is needed!
So what’s the link between orange juice and depression?
The key may be flavonoids which are plant compounds that can influence inflammation, brain signalling, and even the gut–brain axis. This study suggests that what we consume regularly may play a small but meaningful role in mental health alongside sleep, movement, training, and overall lifestyle.
Mental health is multifactorial.
No single food fixes it, but nutrition is clearly part of the bigger picture.
Choi, J. Kim, J.H. Park, M. Lee, H.J. (2023) Effects of Flavonoid-Rich Orange Juice Intervention on Major Depressive Disorder in Young Adults: A Randomized Controlled Trial. Nutrients. [Online] 15 (1). DOI: 10.3390/nu15010145
What do you think?
Do you believe diet can influence mental health?
Would you expect something as simple as orange juice to show an effect?
Save this for later
Like if you enjoy evidence-based fitness & health
Share with someone who loves nutrition science
Comment your thoughts. I read and reply to all of them!
If you want training and coaching that looks at the whole system: movement, nutrition, recovery, and mindset.
That’s exactly what we do at Theory of Fitness.
#fitness #nutrition #depression #orangejuice #personaltraining](https://scontent-sea1-1.cdninstagram.com/v/t51.82787-15/613621820_17992533536871826_8698763919881471163_n.webp?stp=dst-jpg_e35_tt6&_nc_cat=101&ccb=7-5&_nc_sid=18de74&efg=eyJlZmdfdGFnIjoiRkVFRC5iZXN0X2ltYWdlX3VybGdlbi5DMyJ9&_nc_ohc=rio4XKJRmy8Q7kNvwFrI6cF&_nc_oc=AdkeZ0zcnEp6-0lgKH393zbWLzoleOC-WKQyl62ijsAO8a23HZJEXEwJqs7xBLQ6vnE&_nc_zt=23&_nc_ht=scontent-sea1-1.cdninstagram.com&edm=ANo9K5cEAAAA&_nc_gid=5vby89nZqFAMJo5xIRFgPQ&oh=00_AfsBUVsuVJ_X2DkL_Jvn8H3D9kall8doKxr-pDa3cfMP9Q&oe=69880CCF)
![Train smarter - not just heavier.
2025 research shows Velocity-Based Training (VBT) helps you build more power, manage fatigue, and get results.
That means better intent, better feedback, and better gains.
Velocity Based Training research shows: 5% more accurate than traditional %1RM training Predicts strength & power improvements Keeps you explosive without overtraining
Want to know more about how to be the best you? Contact me through my page and we can get started!
#VelocityBasedTraining #VBT #SportsScience #StrengthCoach #PersonalTrainer #Power Training #AthleticPerformance #SpeedTraining #EvidenceBasedTraining #GymScience #strengthandconditioning #PerformanceCoach #TrackAndField #ExplosiveStrength #ScienceOfTraining #SmartTraining #TrainWithIntent #GymTips #FitnessEducation #CoachTips #Insta #Discovery #instagood #fyp
Achermann, B.B. Regazzi, N. Heynen, R. Ludin, D. Suter, J. Drewek, A. Lorenzetti, S.R. (2025) From Monitoring to Prediction: Velocity-Based Strength Training in Female Floorball Athletes. Sports. [Online] 13 (6) DOI: 10.3390/sports13060175
Han, Y. Xie, Y. Zhang, Z- Garcia-Ramos, A. (2025) The effect of velocíty-based resistance training (VBT) on lower limb strength performance in male collegiate boxers: a randomized controlled trial. Front Physíol. [Online] 16 (1) DOI: 10.3389/fphys.2025.1701045](https://scontent-sea1-1.cdninstagram.com/v/t51.82787-15/576535078_17986440029871826_3248862483877244635_n.webp?stp=dst-jpg_e35_tt6&_nc_cat=106&ccb=7-5&_nc_sid=18de74&efg=eyJlZmdfdGFnIjoiQ0FST1VTRUxfSVRFTS5iZXN0X2ltYWdlX3VybGdlbi5DMyJ9&_nc_ohc=HFwMLHsOm1UQ7kNvwFlRfWS&_nc_oc=AdlTHdkkY-Qg9MdpNM45sxfAxdO5nqlI0mwPCKwECHKdaWATcn9GLjDIx9WNIu3NHyY&_nc_zt=23&_nc_ht=scontent-sea1-1.cdninstagram.com&edm=ANo9K5cEAAAA&_nc_gid=5vby89nZqFAMJo5xIRFgPQ&oh=00_Aft1fYKd-Bf_x_-7NMBBwV1pvazL2frcXuRSYEp_r8WMAw&oe=69880FCA)
![Do you know your facts from fiction?
New 2025 research reveals that many'common sense' gym beliefs are actually myths. In a survey of over 700 gym-goers people only correctly identified 5/14 training statements. Think you know your stuff? Take a look at the reference below to see all the questions!
Unger, A. Mosgan, C. Wolte, C. Pettauer, S. Wilke, J. (2025) Knowledge of gym goers on myths and truths in resistance training. Scientific Reports. [Online] 15 (1). DOI: 10.1038/s41598-025-87485-8
And if you or anyone you know is looking for mythbusting with a Sport and Exercise Scientist, you can contact me through my page for personal training.
#StrengthTraining #GymScience #MythBusting #ResistanceWorkout #FitTips #FitnessEducation #2025Research #Northampton #PersonalTrainer #gym](https://scontent-sea5-1.cdninstagram.com/v/t51.82787-15/563398475_17983490732871826_1346010896671362460_n.webp?stp=dst-jpg_e35_tt6&_nc_cat=103&ccb=7-5&_nc_sid=18de74&efg=eyJlZmdfdGFnIjoiQ0FST1VTRUxfSVRFTS5iZXN0X2ltYWdlX3VybGdlbi5DMyJ9&_nc_ohc=hGJCjwH6w_cQ7kNvwHsyjVM&_nc_oc=AdnZwB4GdckiC7k1IIqX77f3lqyxk7Hf7n4n5foeGgyvtGB9gE-yBp3j8tQ1dhlU0cQ&_nc_zt=23&_nc_ht=scontent-sea5-1.cdninstagram.com&edm=ANo9K5cEAAAA&_nc_gid=5vby89nZqFAMJo5xIRFgPQ&oh=00_AfvIN_LeU8T_Hw2ZPTKu-uAFocEPEPnw1S3RA8gImiRUtg&oe=6987FF5F)
What's On Offer
Below you can read up on all the services currently on offer. Whether you are just starting out, looking to develop or even break plateaus and work towards a specific goal there is something for everyone!
Where are we located?
Currently operating out of Selected Fitness. Online Programming and Moblie Training is also remotely available.
Training is available Mon-Fri from 6am-Late, If you would like a different day or time please contact using either the form on the Personal Training page or contact details above.