Complete bollocks. Even if caffeine did in some way allow weight gain, people generally have it when they NEED to be awake, thus are burning more energy. Additionally, there are so many more problems they should be focusing on - soft drinks, juices, and the general fat arses just getting LAZY. Even with coffee, the culture of requiring it faster, easier, simpler is just happening more and more. People find making a cup of coffee too hard, and want a simple pod solution, because they just can't be bothered learning something. In the last hundred years we've gone from needing to do everything manually (cooking etc) to some people not actually knowing how to cook AT ALL. People want Instant coffee and fast food. A cup of coffee is far better for the body than a can of Red Bull, and you don't need a study to prove that. People walk (or drive) into McDonalds to be told boldy on the signage that the average daily intake of energy is 8700kJ, and don't think twice about kicking back a double whopper meal, and better make it a large. As BrettH said above, every body is different, not to mention if you have a desk job, and do absolutely no physical exercise, that daily intake might be closer to 3000kJ to maintain a healthy weight (though you still won't be healthy, you'll just have low body fat - something that people can't seem to grasp). It's now a culture of "I'm getting fat, I'll join a gym! Now I have no time, so I'll eat take away food every night" - the vicious circle goes on.
