Young group of friends eating salad at the dinner table. Image Credit: Jack Hollingsworth/Photodisc/Getty Images

What you eat and how you feel, both mentally and physically, have a close connection. Following a balanced, nutritious diet isn't always easy, cheap or convenient, but it has a significant positive impact on both your short- and long-term health. Eating poorly, in contrast, can tank your energy levels, increase your risk of disease and take years off your life.

Food and Mental Health

Making smart food choices boosts your mental health and your physical health. Balanced diets are associated with lower incidences of depression, anxiety and bipolar disorder, and there is also a link between good mental health and eating whole, unprocessed foods. What you eat also affects how easily you can relax at night and get high-quality sleep. According to nutritional therapist Jo Lewin, large meals and sugary, fatty foods tax your body's digestive system in a way that makes it difficult for you to drift off and sleep well.

Food and Physical Health

Foods packed with vitamins, minerals and nutrients contain a variety of protective substances that can lower disease risks and boost the body's immunity. Including fruits and vegetables in your regular diet, for example, can lower your risk of health problems including cancer, diabetes, stroke, heart attack, heart disease, high blood pressure, bone loss and kidney stones. Healthy diets are also associated with lower overall mortality rates.

Diet and Body Weight

If you've ever gone on a diet or tried to "watch what you eat," you're aware of the intimate link between diet and body weight. High-fiber, low-calorie, unprocessed foods like fruits, vegetables and whole-grains are associated with better weight control, but sugary beverages, processed foods and refined grains are associated with overweight and obesity. In turn, obesity raises your risk of heart disease, high blood pressure, stroke, diabetes, metabolic syndrome, cancer, sleep problems, arthritis and infertility.

Healthy Diet Defined