We receive many questions asking us the difference between certain supplements, how they work and why we sell different varieties of what seem largely the same product. These are all valid questions, and to many seem confusing until you know the answer. The difference between a regular whey protein and a mass gainer per se is that one contains high levels of protein but remains low in carbs, fat and therefore any excess calories, whereas the other is comparatively high in protein, carbs and calories.
If logic suggests to you that the mass gainer supplement, an example would Optimum Health Ultimate Gainer is the one that delivers extra calories, then your logic would be right. For many, it is integral that they achieve an underlying base weight, these people may have struggled for years to gain weight. Consequently a liquid form of calories that is also void of many additives and excess saturated fat is desirable…enter the mass gainer! For others, the thought of gaining weight through excess calories is unthinkable and unnecessary. Some people will already have an underlying level of mass but wish to maintain the lean mass (muscle) without the additional total bodyweight, so a whey protein (or egg, soy, hemp, rice or other source of protein) concentrate or isolate is optimal for this outcome. A good example of a whey protein is Optimum Health Ultimate Whey and XL Nutrition Xtra Whey.
An average mass gainer might deliver between 400-1200 calories per serving, conversely a whey protein is more likely to provide a fraction of this coming in at around 90-140 calories. Regarding protein, the percent of protein is higher in a whey protein but the large serving size needed for mass gainers means you usually get more protein per serving, but less gram for gram.