Genetics is one of the first refuges of scoundrels.
Just as a person can blame their genetics for failure so can a person dismiss their genetics for success. Both cases can be a matter of protecting one's own ego and pride.
Some people are just naturally leaner than others, burn calories better, can achieve better aerobic capacities, distribute fat differently, build muscle more easily, physiologically respond to exercise more effectively, etc.
Some people don't have to monitor their diet like a scientist and they look fantastic whereas others have to be anal about everything they eat and how they exercise to achieve something similar - maybe.
It's just a matter of fact that not everyone is the same. Yes, everyone can benefit from diet and exercise but even if everyone did it 'correctly' it doesn't mean they are going to get the same results as another person. For some people it's not even possible. It's not just about the the food one eats and the exercising one does, it's also about genetics, physiology, and anatomy. To ignore that is being irresponsible and can hurt a person's effort because it can be setting them up for failure that they then blame themselves for and get discouraged when it's something that's not even under their control to begin with.
I've been in competitive sports since I was a little kid and just from observation of fellow athletes I could just see it in people. It's like observing animals that have been breed for certain characteristics. Those with the most desired traits did the best, diet and exercise was secondary. It wasn't just demonstrated in performance but also in appearance.
Diet and exercise only optimize one's effort to reach full genetic potential. It also exposes what they are and where they might also fall short of what a person would like them to be.
Example:Is exercise worth your time? Genes tell When you put in hours at the gym, you expect to get fitter. It turns out, that assumption doesn't hold true for everyone. A new study suggests specific genes may determine, at least in part, how much we really benefit from exercise.
While " benefit from exercise" can mean plenty of things, from slimming down to boosting one's ability to complete a marathon, the researchers specifically looked at what is called VO2 max, or aerobic capacity. This is a measure of how much blood your heart pumps and how much oxygen your muscles consume when they constrict to, say, move your legs on a treadmill.
Bottom line, VO2 max represents your endurance. And this study, detailed today in the Journal of Applied Physiology, suggests a group of 29 genes could potentially categorize individuals into low, medium and high responders to exercise.
A lot of info here more directly:HERITAGE --Genetics, Response to Exercise, Risk Factors
"It is widely recognized that individuals can respond quite differently to a given intervention, such as drugs, diet, or exercise. For instance, there are considerable individual differences in improvement in maximal oxygen uptake (VO2max; measure of aerobic endurance capacity) with aerobic training.
Studies conducted with young or older adults have typically reported gains in VO2max ranging from almost 0% to 50%, even though all the subjects completed exactly the same training program under close supervision. Scientists had previously assumed that these variations result from differing degrees of compliance with the training program, i.e., good compliers have the highest percentage of improvement and poor compliers show little or no improvement. However, it is now clear that even when there is full compliance with the program, substantial variations occur in the percentage improvements in VO2max values of different people. The same principle is also thought to apply to other physical activity-related phenotypes
, including differences in response of the various risk factors for cardiovascular disease and type 2 diabetes.Moreover, previous studies conducted with identical twins have suggested that heredity plays a major role in determining to what degree the body adapts to an intervention such as an exercise training program.
All these data were available by the late 1980s primarily as a result of the research of C. Bouchard and his colleagues at Laval University in Quebec City when the planning for the HERITAGE Family Study began."