In 25 years, we won’t be obsessing about Atkins or South Beach. Nutrition will have changed in ways to make us healthier and happier about what we eat.

Some of the changes will be modest.
Dark chocolate, long recognized as both a rich indulgence and a health food, will dominate stores and homes alike. Milk chocolate will be largely a historical curiosity.
The optimal dose of red wine will be known, and its health effects relative to other libations will be fully elaborated.
At long last, nutritionists will be able to determine the optimal dose of vitamin E. Trans fat will have been eliminated entirely from the food supply. Food-borne infections will have been drastically reduced by use of bacteriophages (viruses that attack bacteria) and radiation.

Of course, this will be after years spent convincing the public that these techniques are indeed safe.
Food labels will have been revised to reveal at a glance the overall nutritional quality of any packaged food. Public school cafeterias will offer healthful foods in two categories: mixed diets and vegetarian. Organic farming will represent more than half of all agricultural productivity in the United States, and 40 percent to 50 percent of the population will be vegetarian.
Some realms of nutrition will have changed much more dramatically.
Nutrigenomics — the prescription of foods and nutrient supplements based on analysis of individual genetic risk factors — will have gone from a dream to a breakthrough analysis to a routine procedure.

Nutrigenomic analysis will be part of a standard medical checkup, culminating in a detailed printout offering tailored recommendations. With this power in their hands, doctors will be reimbursed for offering dietary counseling, and will be able to dispense worthwhile advice.
Functional foods will abound. Insights about nutrient effects on everything from weight and blood pressure to aging, memory and eyesight will have long been used to create bio-engineered "super foods."
The packages of these foods will be emblazoned with claims about the specific genes for which they are designed, in the same way today’s frozen entrees are marketed toward specific diets like low-carb and South Beach.
Multivitamin and mineral supplements will be personalized year-by-year to meet an individual’s needs.

For better or for worse, human breast milk will have been cloned and will be available without the breast. Also, obesity and diabetes rates will have been steadily declining for 15 years.
Of course, some fundamentals of nutrition will remain the same.
Fruits and vegetables will still be good for us, as will whole grains, nuts and seeds, beans, lentils and lean-protein sources.

In the year 2031, parents will still tell their children to eat their broccoli because it’s good for them — that convention won’t go away anytime soon.