Which phase suits you: work it out in five minutes
The right starting point for a protein diet depends on three factors: how much weight you want to lose, how your body currently responds to calorie restriction, and how much daily guidance you need. Someone wanting to shed 5 kg gains nothing from starting in the same phase as someone carrying 30 kg of excess weight. Starting in the wrong place costs you weeks.
Why the starting point matters most
Most people choose their diet phase on gut feeling. That's understandable, since the information about phases is often vague. Yet the starting point is arguably the single most critical decision in the whole process. Begin too strictly and you'll drop out; begin too gently and you'll see zero results after three weeks, and give up.
The Bioteïne 4-phase system only works if you begin in the phase that matches your metabolic situation right now, not the person you hope to be in three months' time. Think of setting your sat nav: you enter your current location, not your destination.
Research from the British Dietetic Association shows that very low calorie diets (under 800 kcal a day) are only effective and safe under clear conditions: sufficient protein intake, at least 50 g of protein a day, and a structured wind-down back to normal eating. That's exactly what a phase system does.
The four factors that determine your starting phase
There's no mystery to working out which phase suits you. You simply look at four concrete measures.
1. BMI or kilograms to lose
This is the most direct criterion. A higher weight-loss target calls for a phase with more structure and lower calorie intake at the outset.
| Weight to lose | BMI (indicative) | Recommended starting phase | kcal per day (phase) |
|---|---|---|---|
| Less than 8 kg | 25-27 | Phase 3 | 1,000-1,200 kcal |
| 8-15 kg | 27-32 | Phase 2 | 800-1,000 kcal |
| 15-25 kg | 32-37 | Phase 1 or 2 | 600-800 kcal |
| More than 25 kg | 37+ | Phase 1 | 500-700 kcal |
Bear in mind that BMI is a blunt measure. Someone with substantial muscle mass can have a BMI of 28 and barely any excess fat. Always combine BMI with your waist measurement and your own sense of body fat percentage.
2. Your experience with calorie restriction
Have you followed a strict diet before? Your body responds differently than that of someone doing this for the first time. Anyone who's been through several crash diets often has a slowed metabolism. In that case, Phase 1 isn't necessarily the best choice, despite a high weight-loss target. Phase 2, with a higher protein intake (at least 80 g a day), often delivers better results in the longer run.
Dieting experience also translates into mental discipline. Someone who knows what hunger feels like and how to manage it copes far better with a strict protocol than someone attempting this for the first time.
3. Activity level and muscle mass
Do you exercise intensely two or more times a week? Then your body needs more protein to preserve muscle mass during weight loss. Sports nutrition research recommends 1.6 to 2.2 g of protein per kilogram of body weight per day for active individuals. During strict calorie restriction, that's difficult to achieve without targeted protein products.
Those who are less active need less protein but also have a lower basal metabolic rate. They tend to lose weight faster in a low-calorie phase, but also face a greater risk of muscle loss if protein intake falls short.
4. Medical situation and medication use
This is the point people most often skip. Type 2 diabetes, thyroid issues, kidney impairment or certain medications (such as blood pressure medication or insulin) all affect how your body responds to a calorie-restricted diet. If in doubt, always consult your GP before starting Phase 1.
The Voedingscentrum advises anyone with a medical condition to seek guidance before beginning a low-calorie diet.
Phase 1 in detail: who is this for
Phase 1 is the most intensive phase. You eat almost exclusively controlled protein products, supplemented with low-energy-density vegetables. Calorie intake sits between 500 and 700 kcal a day, with a protein intake of at least 60 to 80 g. This induces ketosis, a state in which your body burns fat as its primary fuel.
Phase 1 suits you if:
- your BMI is above 32
- you want to lose more than 20 kilograms
- you have no experience with strict calorie programmes but are prepared to commit to full structure
- your doctor gives the go-ahead
Phase 1 is not suitable if:
- you are pregnant or breastfeeding
- you have kidney problems
- you have uncontrolled diabetes
- your BMI is below 25
Average weight loss in Phase 1 is 1.5 to 3 kg a week during the first two weeks, then stabilises to 0.8 to 1.5 kg a week. That initial loss is partly water from glycogen breakdown, not pure fat. Know this beforehand: it's motivating during the first weeks, but the real fat burning kicks in afterwards.
Phase 2: the most commonly used starting phase
Most people who start with Bioteïne fit into Phase 2. In this phase, you take in 800 to 1,000 kcal a day, split between protein meals and a regular evening meal. Your protein intake sits at 70 to 100 g a day, depending on your weight and activity level.
Phase 2 works well if:
- you want to lose 8 to 20 kilograms
- you have little time to cook during the day
- you've followed a diet before with partial success
- you want to eat with the family in the evening
The structure is practical: breakfast and lunch are replaced with protein products from the shake range or meal replacements, while in the evening you cook a proper meal with 150 g of lean protein and vegetables. That gives you freedom without upsetting your calorie balance.
Average loss in Phase 2: 0.8 to 1.2 kg a week after the first two weeks.
Phase 3: slow and sustainable
Phase 3 is designed for two types of people. First: those wanting to lose under 8 kilograms who don't need a drastic approach. Second: those winding down from Phase 1 or 2 and moving towards a more normal eating pattern.
In Phase 3, calorie intake sits at 1,000 to 1,200 kcal a day. You replace one meal a day with a protein product, while the rest is ordinary food focused on lean protein, fibre and minimal refined carbohydrates. Protein intake: 60 to 80 g a day.
Weight loss is slower: 0.4 to 0.7 kg a week. That may not sound like much, but over 12 weeks it adds up to 5 to 8 kilograms. Sustainable, without muscle loss, and with enough energy for everyday functioning.
Take a look at the starter pack for a practical way to structure Phase 3, including meal suggestions per day.
Phase 4: maintenance and lifestyle
Phase 4 isn't a diet phase. It's the exit strategy. After weight loss, the biggest risk is the yo-yo effect. Research published in Obesity Reviews shows that 80% of people who lose weight return to their starting weight within five years, primarily due to the absence of a structured maintenance protocol.
In Phase 4, you use protein products not as meal replacements but as additions. A protein bar as a snack instead of a biscuit. A shake after training. This isn't about restriction; it's about holding on to habits that prevent weight regain.
Calorie intake in Phase 4 is individual: it sits at or just below your total daily energy expenditure (TDEE). For most adults, that's 1,800 to 2,200 kcal a day, depending on sex, height and activity level.
How the phase test works and what it does for you
Self-diagnosis based on an article has its limits. That's why Bioteïne has developed a structured phase test that maps your situation in five minutes. The test asks about your weight goal, BMI, activity level, medical background and previous dieting experience. Based on your answers, you receive a phase recommendation along with a concrete weekly schedule.
The test isn't a medical tool. For a BMI above 40, type 1 diabetes, or active use of weight-affecting medication, the test explicitly refers you to a doctor. That's a deliberate choice: no online protocol replaces medical guidance in complex situations.
After the test, you can move straight on to the high-protein diet guide for the practical detail per phase, including recipe ideas, shopping lists and an explanation of common mistakes per phase.
Common mistakes when choosing a phase
The most common mistake: jumping to a heavier phase too quickly because you want fast results. Phase 1 in week one for someone with 7 kilograms to lose isn't ambitious, it's unnecessary, and it increases the chance of dropping out through hunger, irritability and fatigue.
Another mistake is phase-hopping: switching from Phase 2 to Phase 3 after two weeks because things are going well, then back to Phase 2 a fortnight later because results have slowed. This disrupts your metabolic rhythm. Choose a phase, commit to it for at least four weeks, and evaluate only then.
Finally, failing to account for weekend behaviour. If you follow Phase 1 on weekdays but eat freely at weekends, you're effectively in a hybrid that matches no phase at all. Be honest about your actual behaviour, not your intentions.
The explanation of the 4-phase system goes into more detail on the transition rules and how to determine when you're ready for the next phase.
A realistic timeline per phase
| Phase | Duration (average) | Expected total loss | Transition criteria |
|---|---|---|---|
| Phase 1 | 4-12 weeks | 8-20 kg | Goal reached or doctor advises stepping down |
| Phase 2 | 6-16 weeks | 5-14 kg | Within 5 kg of goal or a stable plateau for 3 weeks |
| Phase 3 | 4-12 weeks | 2-8 kg | Weight goal reached or within 1-2 kg of goal |
| Phase 4 | Indefinite (lifelong) | Maintaining stable weight | No exit criterion: this is the goal |
These timelines are averages. A 50-year-old with an underactive thyroid loses weight differently to a 30-year-old with an active lifestyle. Use the table as a reference, not a guarantee.
For daily support in between meals, protein snacks and protein biscuits are a practical addition in any phase. They keep hunger at bay without upsetting your calorie balance, provided you use them as a replacement rather than an extra.
Frequently asked questions
Can I work out which phase to follow myself, without taking a test?
Yes, based on four factors: weight goal, BMI, activity level and medical situation. The table in this article gives a good indication. For more precise, tailored advice, the phase test points you to the most suitable starting phase based on your personal answers.
How quickly will I see results in Phase 1?
In the first week, you'll typically lose 2 to 3 kilograms, part of which is water from glycogen breakdown. From week two onwards, loss is 0.8 to 1.5 kg a week. Genuine fat burning only begins once the body is fully in ketosis, usually after three to five days.
What if I'm following Phase 2 but barely losing weight?
First check your actual calorie intake, including your evening meal. An evening meal of 700 kcal instead of 400 kcal makes all the difference. If your intake checks out and you see no loss for three weeks, consider stepping down to Phase 1 temporarily, or increasing protein intake to 100 g a day.
Is Phase 1 safe for everyone?
No. Phase 1 is not suitable during pregnancy or breastfeeding, with kidney impairment, uncontrolled diabetes, or a BMI below 25. The BDA advises medical supervision for VLCD programmes at all times, especially where existing conditions are present.
Can I exercise during Phase 1?
Light exercise is fine. Intensive strength training or interval training during the first two weeks of Phase 1 isn't advisable, as energy availability is too low. Walking, yoga or gentle cycling (30-45 minutes a day) is manageable and supports the recovery of insulin sensitivity without risking muscle damage.
When do I move up to the next phase?
When you're within 5 kilograms of your goal, or if you've gone three consecutive weeks without losing weight despite accurate calorie counting. Move up a phase in that case. That sounds counter-intuitive, but a metabolic adjustment sometimes calls for more calories, not fewer.
How much protein do I need per day in each phase?
Phase 1: at least 60 g, preferably 80 g. Phase 2: 70-100 g. Phase 3: 60-80 g. Phase 4: 50-70 g or more with an active lifestyle. The high-protein diet guide gives an overview per phase of products and portions that make these targets achievable.
What do I do if I fall off track partway through a phase due to illness or a holiday?
Pick the phase back up where you left off, rather than starting from the beginning. A break of three to seven days doesn't require a full restart. A break of more than two weeks with unrestricted eating does call for restarting the phase, including the five-day adjustment period.