In the past, researchers looked at the relationship between individual foods and nutrients and health. Today, there is interest in looking at how combinations of foods and beverages, or dietary patterns, impact health. This summary of a NEL review presents what we know about different healthy eating patterns and the amounts, variety, or combination of different foods and drinks, and how often they are eaten affect body weight.

Conclusion

There is moderate evidence that adherence to a dietary pattern that emphasizes vegetables, fruits, and whole grains is associated with modest benefits in preventing weight gain or promoting weight loss in adults.

What the Research Says

• Of the seven studies in the review, the Women’s Health Initiative (WHI), Mediterranean, Vegetarian, and “Healthy” dietary patterns were found to be favorable to body weight outcomes. These healthy dietary patterns consistently included fruits, vegetables, and whole grains. A few studies found that eating less meat helped with body weight. Some studies also looked at the effect of total fat in the diet but found that eating a low-fat diet is not required for weight loss or to prevent weight gain.
• Studies included in this review were short to moderate in length, and persons who closely followed a dietary pattern containing mostly plant-based food had better body weight outcomes.
• More research is needed to find out the exact amounts of food groups that are good to consume. In the mean time, eating a dietary pattern that contains more plant foods and less meat is better for body weight status.

Background

The goal of this systematic review project is to identify patterns of food and beverage intake that promote health and prevent disease. Historically, most dietary guidance has been based on research conducted on individual food components or nutrients. Dietary patterns are defined as the quantities, proportions, variety, or combination of different foods, drinks, and nutrients (when available) in diets, and the frequency with which they are habitually consumed. Different methods of analyses are used to assess dietary patterns including index or score, cluster or factor, reduced rank regression, in addition to other methods, to exam the relationship between adherence to dietary guidelines/recommendations or specific dietary patterns of a population and outcomes of public health concern. The objective of this systematic review was to assess the relationship between patterns of food and beverage intake identified using methods other than index or score, factor or cluster, or reduced rank analyses, and body weight.

Conclusion Statement

There is moderate evidence that adherence to a dietary pattern that emphasizes vegetables, fruits, and whole grains is associated with modest benefits in preventing weight gain or promoting weight loss in adults. (Grade: II-Moderate)

Methods

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 defined using methods other than index factor or cluster analysis and body weight status. Studies that met the following criteria were included in the review: conducted in subjects aged 2 to 18 years; randomized controlled trials, non-randomized controlled trials, or quasi-experimental studies; subjects from countries with high or very high human development (based on the 2011 Human Development Index); subjects who were healthy or at elevated chronic disease risk; published in English in a peer-reviewed journal. The date range was unlimited. The results of each included study were summarized in evidence worksheets (including a study quality rating) and an evidence table. A group of subject matter 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 of effect, and generalizability of available evidence.

Findings

• The Women’s Health Initiative (WHI), Mediterranean, Vegetarian, and “Healthy” dietary patterns were associated with beneficial body weight outcomes. These dietary patterns consistently emphasized fruits, vegetables, and whole grains. Fewer studies considered, but consistently observed benefits, with reduced meat intake. Some studies also considered total fat intake; these studies did not support that targeting a low total fat intake is required for weight loss or stability.
• Studies included in this review were short to moderate in duration, and individuals with greater adherence to the plant-based dietary pattern experienced better body weight outcomes.
• Additional research is needed to quantify the amounts of food groups that are beneficial to consume, but, in general, movement to a dietary pattern with more plant foods and less meat is favorable related to body weight status.

Discussion

The ability to draw strong conclusions was limited due to the following issues:

• Five of the seven studies included in this review assessed dietary intake using food frequency questionnaires. Additionally, one study assessed dietary patterns by using a simple series of questions. These dietary assessment methodologies have measurement error and also prevent sufficient quantification of dietary intake.
• The studies did not consistently consider or report calorie intake and/or energy expenditure, which are important to consider when examining body weight status.