What is whey protein and why is it so effective?
Whey protein, or whey for short, is a fast-absorbing protein released during cheese production. It contains all nine essential amino acids that your body cannot make itself. Thanks to its high biological value and rapid absorption, whey is one of the most well-researched protein sources for preserving muscle and managing weight.
In concrete terms, whey protein has a PDCAAS score (Protein Digestibility Corrected Amino Acid Score) of 1.0, the maximum possible. Compare that with soya at 0.91 or rice protein at 0.47. This score tells you how complete and usable a protein is for your body.
Whey is the liquid by-product left over when milk curdles into cheese. It used to be thrown away. We now know that this "waste product" is actually the most valuable part of the milk for anyone trying to preserve muscle mass during a calorie deficit.
To learn more about using protein strategically during a diet, read the Bioteïne high-protein diet guide.
Concentrate, isolate and hydrolysate: the three types explained
Not all whey is the same. The processing step after the whey is separated determines which type ends up in your tub. This matters if you are lactose intolerant, watching your calories, or simply want the fastest absorption possible.
| Type | Protein per 100g | Fat | Lactose | Absorption | Price |
|---|---|---|---|---|---|
| Concentrate | 60-80g | 2-5g | Present (3-5%) | Moderately fast | Low |
| Isolate | 90-95g | <1g | Virtually none (<1%) | Fast | Medium |
| Hydrolysate | 90-95g | <1g | Minimal | Very fast | High |
Whey concentrate
This is the least processed form. The whey is filtered but not heavily concentrated, which means more fat, more lactose and a lower protein percentage. For people without a lactose intolerance, concentrate is a perfectly good option. Its bioavailability is high and the price is low.
Whey isolate
Isolate goes through an extra filtration step, known as microfiltration or ion exchange. This removes nearly all the lactose and brings the fat content down to under 1g per 100g. The protein percentage rises to 90-95%. This is the most widely used form in quality diet shakes, since it delivers more protein for fewer calories. A 25g serving typically provides 22-24g of protein.
Whey hydrolysate
With hydrolysate, the protein chains have already been partly broken down (hydrolysed) before you drink it, so your body has less work to do. This makes it the fastest-absorbing option. The downsides are the price and a somewhat bitter taste. For weight management, hydrolysate offers no proven advantage over isolate, so you can safely skip it if diet is your sole focus.
Why whey supports weight loss and muscle preservation
The link between whey and weight loss comes down to two mechanisms: satiety and muscle preservation. Both are well documented in the science.
Satiety
Protein suppresses hunger more effectively than fat or carbohydrates. Whey stimulates the release of the satiety hormones PYY (peptide YY) and GLP-1, while lowering the hunger hormone ghrelin. A study published in the American Journal of Clinical Nutrition found that a protein intake of 25-30% of total energy reduced daily calorie intake by an average of 441 kcal, without any deliberate restriction. Source: AJCN 2005, Weigle et al.
Muscle preservation during a calorie deficit
When you eat less than you burn, your body risks breaking down muscle mass for energy, which is something you want to avoid. Muscle raises your resting metabolic rate, meaning you burn more even while doing nothing. Whey, specifically because of its high leucine content (2.5-3g per 25g serving), activates the mTOR signalling pathway, the molecular trigger for muscle protein synthesis. Even without hitting the gym, leucine helps preserve muscle protein during a diet.
A 25g serving of whey isolate provides, on average:
- 22-24g protein
- 100-115 kcal
- 2.5-3g leucine
- less than 2g fat
- less than 3g carbohydrates
This profile makes whey especially efficient in a calorie-restricted diet. You hit your protein targets without blowing your calorie budget.
Want to know which protein target suits your situation? Take the Bioteïne phase test for personalised advice.
Whey and lactose intolerance
This is a frequently asked question, and the answer is nuanced. Whey concentrate still contains 3-5% lactose per 100g, which can cause symptoms in people with a lactose intolerance, such as bloating, gas or cramps.
Whey isolate contains less than 1g of lactose per 100g, sometimes under 0.1g per serving. Most people with a moderate lactose intolerance tolerate isolate well. In cases of severe intolerance, or a cow's milk allergy (a different condition entirely), whey is best avoided altogether. A cow's milk allergy is an immune response to milk proteins (casein or whey), whereas lactose intolerance is a digestive issue.
Not sure whether whey is right for you? Speak to your GP or a dietitian. The British Dietetic Association offers clear guidance on lactose and diet: BDA: Protein.
Plant-based alternatives to whey
If you don't or can't use dairy, there are options, but it's worth being honest about their limitations. Most plant proteins have a lower leucine content and a lower PDCAAS score than whey.
The best plant-based alternatives are:
- Pea protein: PDCAAS 0.69, low in methionine but high in arginine. Easily digested.
- Soya protein isolate: PDCAAS 0.91, a complete amino acid profile, though hormone-sensitive for some people.
- Rice and pea combination (80/20): combining the two means the amino acid profiles complement one another, with leucine content rising to roughly 2g per 25g serving.
In practice, if you want the same muscle-preserving effect as whey isolate, you'll need to increase your plant-based protein serving to 30-35g to reach a comparable leucine level (2.5g). That's 5-10g more powder per shake, which affects both calories and taste.
Bioteïne also offers plant-based options. Browse the shake collection for the full range.
How much whey per day is realistic?
There's no magic number. The right amount depends on your overall protein target, your body weight and how much protein you're already getting from regular food.
The standard recommendation for someone losing weight while preserving muscle mass is 1.6 to 2.2g of protein per kilogram of body weight per day. At 80kg, that's 128 to 176g of protein a day.
A realistic distribution might look like this:
- Breakfast: 25-30g protein from cottage cheese, eggs or a protein shake
- Lunch: 30-35g protein from meat, fish or pulses
- Snack: 20-25g protein from a shake or protein bar
- Dinner: 35-40g protein
In this schedule, one serving of whey isolate (25g of powder) provides 22-24g of protein. That covers one eating moment but doesn't replace a full diet on its own. Two shakes a day is achievable and sensible. More than three is rarely necessary if your regular meals are well structured.
The British Dietetic Association recommends spreading protein intake across several meals for optimal absorption and muscle protein synthesis: BDA: Protein.
For a full overview of daily protein targets per phase, read the Bioteïne high-protein diet guide.
Bioteïne shakes: whey within a diet structure
A bag of loose whey powder is one thing. A shake designed to fit within a structured weight-loss programme is another matter entirely. Bioteïne shakes are developed as meal replacements within a multi-phase system, not as sports nutrition.
That difference shows up in the details:
- Each shake delivers 25-30g protein per serving
- Calorie content: 180-220 kcal per serving
- Fortified with vitamins and minerals so you don't run short when replacing meals
- No added sugar, no artificial colourings
The shakes fit within the Bioteïne 4-phase system, which guides you step by step from an intensive starting phase through to sustainable weight maintenance. Each phase has its own protein ratio and calorie target.
Ready to get started? Check out the starter pack or the full shake collection. You can also mix in individual products such as protein bars, protein meals or protein snacks for more variety throughout the day.
Frequently asked questions
What's the difference between whey protein and whey?
Whey protein and whey are the same product. "Whey" refers to the liquid by-product of cheese production and its associated protein. Both terms refer to the same fast-absorbing milk protein with a complete amino acid profile and a biological value of around 104.
Does whey really help with weight loss?
Whey helps indirectly. It boosts satiety through hormone release (PYY, GLP-1) and helps preserve muscle mass during a calorie deficit. Muscle mass raises your resting metabolic rate. Whey doesn't burn fat by itself, but it makes sticking to a calorie deficit easier and more physiologically efficient.
Which is better for a diet: whey isolate or concentrate?
Isolate is the better choice for dieting. It delivers 90-95g protein per 100g versus 60-80g for concentrate, contains barely any lactose, and has less than 1g of fat. You get more protein for fewer calories. Concentrate is cheaper, but less efficient per calorie.
Can I use whey if I'm lactose intolerant?
Whey isolate contains less than 1g of lactose per 100g, sometimes under 0.1g per serving. Most people with a moderate lactose intolerance tolerate it well. Whey is best avoided if you have a cow's milk allergy, since that's an immune reaction to the protein itself, not to the lactose.
How many grams of whey a day is safe?
For healthy adults, the standard advice is 1.6 to 2.2g of protein per kilogram of body weight per day. At 80kg, that's a maximum of 176g of total protein a day, from all sources combined. Two servings of whey (44-48g of protein together) is safe and sensible for most people within that total.
Is plant-based protein just as good as whey?
Plant protein has a lower PDCAAS score and less leucine per serving than whey isolate. A combination of pea and rice protein comes closest. To achieve the same muscle-preserving effect, you'll need a 5-10g larger serving. Not worse, but it does require more attention to dosage.
When is the best time to take whey?
Timing matters less than your total daily intake. That said, spreading intake across several eating moments (every 3-4 hours) is preferable to one large serving, as this maximises muscle protein synthesis. A serving as a breakfast replacement or snack works well in practice.
What's in Bioteïne shakes besides whey?
Bioteïne shakes combine whey isolate with the vitamins and minerals you need when replacing meals. They contain no added sugar and no artificial colourings. The exact composition varies by product and can be found on the product pages within the shake collection.