Nutritional advice is critical in the management of metabolic syndrome. Most clinicians, however, are not well informed about the principles of healthy eating. Healthcare professionals should learn the latest research and recommendations concerning carbohydrates, fats, and protein. With this information, one can provide useful advice to patients about healthy eating.

One of the most important components relating to nutritional advice for patients who are overweight is reduction of calories. Patients should understand that the energy stored in food is measured in terms of calories. One calorie is the amount of energy required to raise the temperature of 1 gram of water 1°C. Most people's daily caloric requirement is less than 2,000 calories. As a quick rule of thumb, patients can calculate the number of daily calories they require by multiplying their current weight in pounds by 13 (or 15 if one is active). Patients who are overweight should reduce the number of consumed calories in order to lose weight. Reduction in calories is the most important dietary component of weight loss.

When recommending reduction in calories, specific guidelines should be kept in mind. Patients with a BMI between 27 and 35 should reduce their total calorie intake by 300–500 daily. Patients with a BMI greater than 35 should reduce their total calories by 500–750 daily [7]. This reduction will produce the recommended weight loss of 1–2 pounds per week in most patients.

Portion control is also a key to weight loss. Portion control has been shown to produce the greatest weight loss in women over a 24-month period, more than reduced dietary fat consumption, increased fruit and vegetable consumption, or increased physical activity [8]. Thirty-eight percent of obese patients who consistently practiced food portion control lost 5% or more of their baseline weight, while 33% of patients who did not consistently practice portion control gained 5% or more of their baseline weight. A 2006 study by the same researchers involving overweight and obese men showed that using controlled portions of food led to more weight loss than a self-selected diet based on the food guide pyramid [9]. (Note: The historical food guide pyramid is considered obsolete.)

Since the 1990s, the Institute of Medicine (IOM) has issued a series of reports that suggest dietary reference values for intake of nutrients. One of these reports, updated in 2005, establishes the Dietary Reference Intakes (DRI) for energy, carbohydrates, fiber, fat, fatty acids, cholesterol, protein, and amino acids. The following ranges are recommended in the 2005 report for percentage of daily caloric intake [11]:

With all the publicity regarding various diets, patients should be advised that it is as important to include certain foods as it is to exclude others. "Fad diets" typically exclude certain foods and therefore often have nutritional deficiencies. For example, high-fat, low-carbohydrate diets are low in vitamin E, vitamin A, thiamin, folate, calcium, magnesium, and zinc. Low-fat diets are typically deficient in vitamin B12. Additionally, a meta-analysis and systematic review of long-term studies of low-fat, high-protein diets found no net benefit on outcome markers of obesity, cardiovascular disease, or glycemic control [12].

Instead of counseling patients about specific diets, it is more useful to focus on healthy eating.

The 2025–2030 Dietary Guidelines encourage Americans to adopt eating patterns centered on nutrient-dense foods, including [10]:

The following quantitative recommendations remain important components of a healthy dietary pattern [10]:

Currently, Mr. G snacks on sugary treats throughout the day, as he does not take time to eat breakfast and frequently goes without lunch. By the time he eats dinner, relatively late in the evening, he is famished and tends to overeat. Mr. G has very little nutritional information about the food he eats. Either the physician can provide some basic dietary information, or the patient can be referred to a dietitian. The goals of dietary counseling for Mr. G would be: