A few words about us

Mateja and Jacqueline

Creators of Gainsayer Fitness

We’re a young, fitness-inspired couple living in Serbia. Mateja was born and raised here, whereas Jacqueline relocated from the US several years ago.

Though we have very different life experiences, we share the desire to provide authentic perspective and advice to other people like us, no matter where they live and what resources they have access to.

Inspired by fitness and the pursuit of a healthy lifestyle, we decided to share some of our thoughts, experiences, and results that we achieved over the years.

Our blog will cover anything fitness related and, in no particular order, we’ll be talking about training, nutrition, and other things related to becoming (and staying) healthy.

Our aim is to inspire and help people achieve their fitness goals by sharing our experiences and experiments. We hope to give you a clearer picture of what your expectations should be in pursuit of your goals, whether you’re a fitness fanatic or just looking to make a change in your lifestyle.


  • Going to the gym, lifting weights, exercising in any way - no mam(sir)! That was not my thing. Mateja was my first trainer, he introduced me to all those things. Going from 0 to 100 (to be honest 90kg) in less than a year for squat and sumo-deadlift was unthinkable for me, but we did it. When I changed the gym, other trainers started complimenting my form while performing these exercises - which should be a huge recognition for Mateja. Last but not the least, Mateja is really flexible and ready to adjust, so when I went on vacation, I just sent him images from the hotel’s gym and he created training sessions that I can perform in that gym. He is really passionate and dedicated, it was a pleasure working with him!
    Maja Isakov
  • Growing up overweight, I only started exercising at the age of 25, back in 2017. I went on keto for 4 months–Mateja introduced me to the diet and created a special workout plan for me which I followed religiously. I lost around 15 kilos but that was it–I stopped training and eating healthy and ended up gaining even more weight. Last summer I contacted Mateja again and asked him to be my personal trainer, knowing that he was the best person to help me get in shape. 8 months later and here I am: obsessed with deadlifts and 20 kilos lighter. Mateja has been nothing but supportive. He helps me push the boundaries and believe in myself. I couldn’t imagine a more passionate, easy-going and dedicated trainer than Mateja!
    Elizaveta Trefilova