I think that a disciplined childhood makes it more possible to give a child a greater chance of having a healthier life, though of course there are some diseases that are completely unrelated to causes such as nutrition and wellbeing, and can strike anybody. Factors such as diet and psychological wellbeing and happiness are of course crucial factors that go into making somebody healthy or not, and so ensuring that a child is fed properly and reared in an atmosphere of love is very important.
It's possible to argue that children who are required to exercise regularly are less likely to suffer from heart problems, obesity, diabestes, and other such medical issues than children who do not face such requirements. Similarly, it's possible to argue that children who are required to eat healthy diets are also less likely to suffer from such problems. Interestingly enough, the site listed below, which stresses the benefits of a disciplined, military-style education, does not obviously stress the physical benefits of such an education, although one might have expected it to do so:
If a child chooses for him/herself to follow a diet or pattern of physical activity that leads to healthy habits, that could be considered a positive form of a disciplined childhood. I don't know of many children who would consistently choose such a lifestyle, but I don't like some of the connotations that arise in my mind when I read "disciplined childhood" and I don't agree that such a regimen, whether self-imposed or enforced by someone else, will guarantee that no lifestyle disease will occur at a later point. Second-hand smoke, for example, can lead to lung cancer regardless of activity or diet.
I think that you could argue either side of this statement, depending on how the discipline is provided. Research shows that people who eat a healthy diet and maintain a healthy body weight are definitely at lower risk for type II diabetes and heart disease, which are two of the best-studied lifestyle diseases, later on in life. Consequently, you could argue that children who grow up with good eating habits are less likely to develop these diseases, provided they continue to embrace those eating habits in adulthood.
However, too harsh a home life, with too much emphasis placed on healthy eating and/or maintaining a certain weight, could easily backfire. Children raised in an overly restrictive environment may be more apt to overeat or otherwise self-indulge when they are living on their own. Consequently, I would have to say that a childhood during which one is educated about caring for ones body is much more likely to be successful than one where self-care is imposed and is seen as a form of discipline.
I think that there is too much vagueness in the statement to prompt a clear affirmation or negation of it. On one hand, the term "disciplined" means so many different things to so many different people. This is vague and imprecise, at best. Cultural norms, individual choice, and nurturing paths are always difficult to quantify and I think that this is one instance where there is not much in way of exception. At the same time, I think that a full embrace of the idea of "lifestyle diseases" is needed. If the term refers to diseases that end up resulting in social orders where life is prolonged, then it seems to me that there is some level of tension in the statement. "Disciplined childhood" indicates some level of personal choice and action can be taken, while "lifestyle diseases" seem to be more on a scale of inevitability that lie outside of the realm of individual choice. For example, Alzheimer's Disease research indicates little in way of absolute prevention of the condition. I do think that there are ways in which children can be introduced to effective dietary habits as well conditions of patterns of life that represent wellness. There is little to indicate that this would hurt children and much to indicate that this would provide great benefit to them. Yet, I think that the idea of "aversion" to lifestyle diseases is a bit too strong, especially when there are different causation that lie within them. In the end, I come back to the "disciplined childhood" element in causing me some level of hesitation in fully embracing the statement. Perhaps, I could be swayed more with something like "effective education in childhood about health conditions linked to diet and actions that enhance a physical and mental state of wellness." The concept of "disciplined childhood" is too subjective for me and something that I don't necessarily see in the literature or research.