Lean Startup expert / Growth Hacker, JJF Consultancy
2015 - now

As a Growth Hacker, I implemented and instructed the use of tools like Mixpanel, Kissmetrics, Optimizely, Hotjar, Automate Ads among others in Sanoma. I Developed and productized two workshops based on the books Traction and Hooked. Furthermore I developed and invented various Sprints with brands like, SNS Bank and Europcar. The Innovation Sprint is a workshop inspired by Google’s Product Design Sprint, where the first stage of a new business is tested and staged within three days.

Menu Engineer / Founder, Data Chefs

At Data Chefs we set up marketing automation for restaurant owners. The main goal was to increase reservation and return visits. Furthermore, we did A/B testing and costing of their offline and online menu’s, optimising for more revenue.

Founder, Twente Kiest Zelf / Nederland Kiest Zelf
2014 - 2016

Twente Kiest Zelf and Nederland Kiest Zelf are lead generation websites for fiber internet connections. When it became imminent that 80,000 households had to change internet provider, within one week, I launched a website to sign up customers for collective buy-in of fiber internet. I organized a blind auction between Internet Service Providers for everyone who was part of the collection. Grew our email database to 15,000 with a very small marketing budget. Our main traction channel was PR and social media. ROI on this campaign was more than 20. Setup Nederland Kiest Zelf in a different province, based on learning with Twente Kiest Zelf. Grew a database of 10,000 addresses using email marketing, social advertising and door to door sales.

Lean Startup expert / Growth Hacker, Sanoma Lab
2012 - 2015

At Sanoma, a leading media and learning company in Europe. I was responsible for developing and establishing new business in a data driven way. To accomplish this, I helped with the setting up of the Sanoma Lab. Using the lean startup methodology, we initiated and aided growth of 15 business ventures. Amongst them Swipe & Shop, Weekmenu, BeautyTale and ClipScool. The ideas came from people in the business and from participants in the internal accelerator programs. Depending on the need of the ventures, I did customer surveys, online marketing and business development. We set up a growth team to advise other titles and brands within Sanoma. I did over 300 customer interviews in person and innumerable number online. I did project management for two accelerator programs, both with around 400 participants. One was a joint effort with KPN, the largest Telco of the Netherlands. The other focused on education and took place in 5 countries simultaneously throughout Europe.

Online Marketeer, Sanoma Media
2011 - 2012

At Sanoma Media, I was responsible for running the digital magazine website and app of I was also responsible for acquiring and educating new customers. I set up an online and offline marketing campaigns with a budget of 200,000 euros.

Editor, Talpa Media

Talpa Media is the production company of John de Mol, which is responsible for shows like The Voice of Holland. I was responsible for the content creation of three different TV-shows, with an audience of 2 million. Making the shows was a real team effort. I got an experience in communication and handling busy, pressurizing schedules.

Attorney-at-law, Loyens & Loeff N.V.
2010 - 2011

At the Banking & Finance section of Loyens & Loeff, the biggest law firm in Netherlands, I drafted securities for big transactions. I gave legal advice on commercial loans and secure lending and did litigation in the fields of intellectual property and labor law.


85 %
Conversion Optimisation
100 %
Lean Startup
95 %
Growth Hacking
100 %
Public speaking
99 %
Workshop facilitation
95 %
65 %
65 %
60 %
40 %
40 %
70 %


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Lea Kroft
Innovatie Manager at SNS Bank

Justus heeft als facilitator een innovatie sprint begeleid en hij deed dit vol enthousiasme. Hij was goed voorbereid, goed geinformeerd en zorgde voor voortgang. Door de tijdslijnen goed in de gaten te houden hadden we na 3 dagen, 2 mooie concrete ideeen, waarvan er meteen 1 live ging om te testen. Door het gebruik van bepaalde methodieken, duidelijke time slots en vooral veel enthousiasme kwamen we in 3 dagen tot een resultaat die ik vantevoren niet had kunnen bedenken. Dus wil je resultaat, kennis en energie dan moet je bij Justus zijn!

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Marc Rijken
Innovatie Manager bij SNS Bank

Met de nodige ervaring en enthousiasme heeft Justus de innovatiesprint van SNS en Sanoma geleid. Door strak te zijn op het proces en los op de inhoud, kwam de inhoud "vanzelf". Hij wist de juiste methodes te gebruiken om het creatieve in ons los te krijgen en binnen 3 dagen te komen van doelgroep tot compleet afgerond live concept met validatiecampagne en pitch presentatie.

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Sanne Linssen
Digital Coördinator VIVA at Sanoma NL

Samen met mijn team heb ik de workshop 'Hooked' gevolgd bij Justus. Een leuke en inspirerende ervaring. Door middel van creatieve oefeningen en brainstormsessies leert Justus je je vaste denkpatronen te doorbreken, wat leidt tot interessante en bruikbare inzichten. Justus weet waar hij het over heeft en houdt de snelheid in de sessie. Wij zijn de deur uitgelopen met een hoop nieuwe ideeën en directe handvaten om ons merk te versterken. Bedankt!

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Ewoud Uphof
Conversion specialist

Justus has a lot of knowledge about growth hacking. He knows his theory, but more importantly he knows how to put the theory in practice. Within the Sanoma Innovation Lab he shares knowledge with in-depth workshops about growth, lean start-up and traction.

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Evelien Van Der Geest
Sr. Program Manager Organisational Effectiveness (Employee Engagement & Development, Performance Mngt, Change Mngt)

I’ve participated in a design sprint organised by Justus. The sprint was both fun and very informative, all in all a great experience! Justus really moves the sprint forward and is able to keep an eye on the ball. He keeps people aware of the process and focused on the end goal. Both his knowledge and his positive attitude make Justus a very pleasant person to work with!

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Olof Hoverfält
Principal Consultant, Digital Business Development

I participated in a 3-day intensive design sprint co-organized by Justus at the Sanoma Lab. Justus did a great job actively participating in development, steering team focus to the essentials and pushing progress to successfully produce not only an excellent sprint deliverable, but an outstanding learning experience.

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Leonie van de Laar
Visual / UX Designer, Telfort

I've worked with Justus at the Sanoma Lab from the very beginning of the Lab in back in 2013. Justus is a very skilled growth hacking professional, with an supremely talent for training people and public speaking. Justus hosts Growth Hacking and Design Sprints in an extremely energetic way. For example the Design Sprint 'How to design habit forming products' by using The Hook by Nir Eyal changed my view on Product Design from then on. And last but not least, Justus is a great colleague to have a laugh (and a beer) with.