The bar and beverage market started out aimed at serious sportspeople, but has been moving ever more mainstream over the past five years.
Research and intelligence provider Leatherhead International set the total market value for performance foods and drinks at $19.37 billion this year, representing 50 percent growth in the past five years.
However according to the Australian Institute of Sport, only specific groups of serious athletes may need extra protein on occasion - such as endurance athletes who need between 1.2 and 2g of protein per kg of body weight per day, strength-trained athletes who need between 1.2 and 1.7g, and adolescent athletes who need 2g per kg per day.
For normally active people, the maximum protein requirement is just 1g per kg - and even less for those who are sedentary.
A recent National Nutrition Survey showed that on average, men were gleaning 1.9g of protein per day from their normal diets, and women 74g. For people of average weight (80kg men, 65kg women), this means that there is no need to source additional protein from specialist products.
In its Choice magazine, the association published nutritional data of 40 protein bars and beverages. Nutritional content varied from 5g of protein per 28g serving for Powerbar Pria (mint chocolate), to 45g per 100g serving for Aussie Bodies HPLC Bar (chocolate).
It warned that protein consumed in excess of that needed to grow and repair the body is used to provide energy - and any that exceeds energy requirements tends to be stored in the body as fat.
This means that consumers who think they are making a healthy choice by consuming protein bars and taking moderate exercise may, in fact, end up putting on weight.
The report also criticised marketing claims on products, such as "Feed your potential", "To help you perform at your best and surpass your goals", and "Helps build and maintain muscle tissue for up to six hours".
On the surface, these statements may be aimed at professional athletes, for whom small differences could yield results in competition. But it said:"It's just as easy for recreational athletes to succumb to marketing hype. But not all the claims on protein bars can be substantiated."
In particular it drew attention to additional amino acids, the 'building blocks of protein' in products, and compounds like creatine and L-carnitine that are intended to boost metabolic processes.
In the case of creatine, it said there are "varying levels of scientific support for the benefit", and none for carnitine.
Moreover, "considering that foods can usually provide amino acids in the amounts required, there's little to be gained from buying products with them added".
Consumers should also be wary of "jazzed up", scientific-sounding proprietary names for protein, like MLO's Biocytein and EAS's Mypro2, which give the impression that some types of protein are better than others. In fact, whether from whey, soy or something else, it says there is not enough evidence to suggest any source is better than any other.
The report does concede that bars and beverages may make more convenient snacks than food protein sources like sandwiches or smoothies - and indeed can be a better nutritional option than confectionery such as Mars bars.
But although most of the bars tested had less sugar and fat than a Mars bar, a third had more kilojoules.
"That and their comparatively high price are good reasons for having protein products as an occasional snack only," said the association. Price per bar can be as high as A$6 (c €3.55).
In an interview with NutraIngredients.com earlier this year, Leatherhead marketing intelligence business manager Susie Johnson said that, in some markets such as the US, energy bars are entering a phase of maturity.
But she agreed that that so-called sports drinks are no longer aimed purely at sportspeople, but at sporty and health-conscious general consumers.
While these consumers may not need the levels of energy contained in the products if they are not doing a strenuous work out each day, they might need more energy as they are trying to fit more into the day. "It is a different kind of energy", she said.
"A key consumer concern is tiredness and products with energy may help to alleviate tiredness."