What is the relationship between adherence to dietary guidelines/recommendations or specific dietary patterns, assessed using an index or score, and measures of body weight or obesity?
The goal of this systematic review project was to identify dietary patterns of food and beverage intake that promote health and prevent disease. Dietary patterns are defined as the quantities, proportions, variety, or combination of different foods, drinks, and nutrients in diets, and the frequency with which they are habitually consumed. Researchers have used scores (or indices) to measure adherence to healthy dietary patterns, such as a Mediterranean style diet, or adherence to dietary guidelines. The scores are then used to examine associations between a given dietary pattern and health outcomes. Because of the increased prevalence of overweight and obesity in the United States, with associated co-morbidities, it is important to determine which dietary patterns may be associated with prevention or decreases in obesity, and how this information can be translated to nutrition policy recommendations. The objective of this systematic review question was to determine the association between adherence to a specific dietary pattern, assessed using an index or score, and measures of body weight or obesity.
There is moderate evidence that, in adults, increased adherence to dietary patterns scoring high in fruits, vegetables, whole grains, legumes, unsaturated oils, and fish; low in total meat, saturated fat, cholesterol, sugar-sweetened foods and beverages, and sodium; and moderate in dairy products and alcohol is associated with more favorable outcomes related to body weight or risk of obesity, with some reports of variation based on gender, race, or body weight status. (Grade: II Moderate)
Literature searches were conducted using PubMed, Embase, Navigator (BIOSIS, CAB Abstracts, and Food Science and Technology Abstracts) and Cochrane databases to identify studies that evaluated the association between dietary patterns (using an a priori
index or score) and risk of obesity. Studies that met the following criteria were included in the review: randomized controlled trials, non-randomized controlled trials, or prospective cohort studies; subjects aged 2 to18 years; subjects who were healthy or at elevated chronic disease risk; subjects from countries with high or very high human development (2011 Human Development Index); and published in English in peer-reviewed journals. The date range was unlimited. Diet exposure was assessed by adherence to a hypothesis-based dietary pattern, defined using a numerical scoring system.
A group of technical experts were involved in a qualitative synthesis of the body of evidence, development of a conclusion statement, and assessment of the strength of the evidence (grade) using pre-established criteria including evaluation of the quality, quantity, consistency, magnitude o f effect, and generalizability of available evidence.
- Fourteen studies met the inclusion criteria for this systematic review and the body of evidence consisted primarily of large prospective cohort studies. Two major categories of diet exposure were identified: Mediterranean style and dietary guidelines-related dietary patterns.
- Adherence to a Mediterranean diet score or a dietary guidelines-related score was associated with decreased risk of obesity, with some reported variation based on gender or body weight status.
- Adherence to a Mediterranean diet score or a dietary guidelines-related score was associated with decreased body weight, BMI, waist circumference, or percent body fat, with some variation based on gender and race.
- Mediterranean or dietary guidelines-related dietary patterns share many beneficial characteristics and generally reflect a plant-based, minimally processed, nutrient-dense dietary pattern. Consistent components across the scores were beneficial foods including vegetables, fruits, whole grains, legumes, and sources of unsaturated fats (particularly fish); foods that were beneficial in moderation including dairy products and alcohol, and foods and nutrients presumed to be detrimental including total meat, saturated fat, cholesterol, sugar-sweetened foods and beverages, and sodium.
The scores that were associated with decreased risk of obesity were the Mediterranean Diet Score (MDS), the relative Mediterranean Diet Score (rMED), the Healthy Eating Index (HEI)-1995 and a customized HEI-2005, the Diet Quality Index–International (DQI-I), the Dietary Guidelines Adherence Index (DGAI), and the French Programme National Nutrition Santé Guideline Score (PNNS-GS). Taken together, the positive components of scores that were associated with decreased risk of obesity were fruits, vegetables, whole grains, legumes, and fish. Alcohol was commonly included as a positive component when consumed in moderation. Meat and dairy, with some variations, were negative components in Mediterranean scores or recommended within specific ranges for dietary guidelines indices. The dietary guidelines indices also included saturated fat and cholesterol, or added non-vegetable fats, as negative components above a specified level of intake. Sugar-sweetened food and drink components were included and scored negatively in most of the dietary guidelines indices. Overall, there were a large variety of dietary pattern scores used that were difficult to compare because foods were aligned, described, or scored in dissimilar ways.