Salmon is a rich source of high-quality protein and provides plenty of "good" fats: omega-3 fatty acids. A diet rich in omega-3 fatty acids helped people feel more satisfied when they were watching their calories, per a study in Appetite. Eating salmon can be a delicious and versatile way to get your recommended two weekly servings of heart-healthy fish.
In addition to dietary recommendations for the general population, there are many specific diets that have primarily been developed to promote better health in specific population groups, such as people with high blood pressure (as in low sodium diets or the more specific DASH diet), or people who are overweight or obese (in weight control diets). However, some of them may have more or less evidence for beneficial effects in normal people as well.
Stephen Colbert may be on to something. UCLA Center for Human Nutrition researchers divided study participants into two groups, each of which were fed a nearly identical low-cal diet for 12-weeks. The only difference between the groups was what they were given to eat as an afternoon snack. One group ate 220-calories of pretzels while the other group munched on 240-calories worth of pistachios. Just four weeks into the study, the pistachio group had reduced their BMI by a point, while the pretzel-eating group stayed the same, and their cholesterol and triglyceride levels showed improvements as well.
For people who are healthy, a healthy diet is not complicated and contains mostly fruits, vegetables, and whole grains, and includes little to no processed food and sweetened beverages. The requirements for a healthy diet can be met from a variety of plant-based and animal-based foods, although a non-animal source of vitamin B12 is needed for those following a vegan diet. Various nutrition guides are published by medical and governmental institutions to educate individuals on what they should be eating to be healthy. Nutrition facts labels are also mandatory in some countries to allow consumers to choose between foods based on the components relevant to health.