Almonds are a great source of mono- and polyunsaturated fats, which can help lower your cholesterol and keep you slim. They also contain fewer calories than most other varieties of nuts (just 163 calories for 23), as well as plenty of fiber and vitamin E. According to a study in the International Journal of Obesity, people who added a daily serving of almonds to a low-calorie diet lost more weight than those who followed the same diet but ate a carb-heavy snack such as crackers instead.
Not all the nutrients and other substances that contribute to good health have been identified, so eating a wide assortment of healthy whole foods like fruits and vegetables helps ensure that you get all of the health-promoting benefits that foods can offer. If your diet, day after day, consists of the same half dozen foods, it could fall short. In addition, varying your food choices will limit your exposure to any pesticides or toxic substances that might be present in particular foods.
The weight of evidence strongly supports a theme of healthful eating while allowing for variations on that theme. A diet of minimally processed foods close to nature, predominantly plants, is decisively associated with health promotion and disease prevention and is consistent with the salient components of seemingly distinct dietary approaches. Efforts to improve public health through diet are forestalled not for want of knowledge about the optimal feeding of Homo sapiens but for distractions associated with exaggerated claims, and our failure to convert what we reliably know into what we routinely do. Knowledge in this case is not, as of yet, power; would that it were so.