It's a sad reflection of modern lifestyles that personal training and obesity often go hand in hand. As the field increasingly mirrors the trends in modern society, this is something that all health professionals need to be prepared to deal with.
There is little doubt that we are in the midst of an epidemic caused by sedentary lifestyles and poor dietary choices. It is estimated that almost 25% of UK adults are now obese, with a further 40% overweight - in fact, those who are not either overweight or obese are now in the minority!
Thus it makes perfect sense that personal training and obesity would go together. When people seek the services of an exercise professional, losing weight is often high on their list of priorities. For professionals working in personal training and obesity, the challenge, however, is not simply to devise a program that will help people lose weight, but to come up with something that they will actually stick with.
Any good exercise professional should be able to devise a program that burns body fat - the problem is that by the time people have gained enough weight to be considered obese (technically defined as a BMI of 30 or above), they have developed a range of habits that are supporting their weight gain.
Simply telling them to exercise more is usually not going to wash. The skilled practitioner has to address a culture or mindset in which sedentary activities are the norm, exercise is considered a form of torture, and overeating and poor food choices are part of everyday life.
To operate in a vacuum in which you assume that simply having someone do a designated workout three times a week will solve all their problems is naive, and likely to lead to failure.