Study finds no link to obesity with moderate intake

New research debunks myths around eggs and obesity, showing how moderate consumption supports health while highlighting the best cooking methods for maximum nutritional benefits.

Study: Association between egg consumption and risk of obesity:a comprehensive review: EGG CONSUMPTION AND OBESITY. Image Credit: MasAnyanka / Shutterstock

In a recent review published in the journal Poultry Science, researchers conducted a comprehensive review to elucidate if frequent egg consumption can increase obesity risk in healthy humans. They reviewed two decades of nutritional literature between 2002 and 2022 and found that most egg-derived nutrients (lecithins, apolipoproteins, and unsaturated fatty acids) are not associated with increased obesity risk. Surprisingly, most research suggests that these nutrients reduce the probability of obesity via lipid metabolism regulation. The review also noted that individual responses to dietary cholesterol vary, with some people classified as “high responders” who may experience significant changes in cholesterol levels, underscoring the importance of personalized dietary advice.

Notably, the selection of cooking method was found to substantially alter the nutritional composition of eggs, thereby significantly affecting their physiological outcomes on human health. Specifically, soft-boiled eggs were identified as the optimal method, retaining the most beneficial nutrients compared to hard-boiled or fried eggs. In summary, seven to eight eggs per week were not associated with increased obesity risk in healthy humans.

Background

Obesity is one of modern society’s foremost public health concerns, with the World Health Organization (WHO) estimating that one in every eight humans live with the condition. The condition is characterized by unnatural weight (body mass index [BMI] > 30). It is associated with numerous chronic and potentially life-threatening diseases, including cardiovascular diseases (CVD), type 2 diabetes (T2D), liver diseases, and certain cancers.

Alarmingly, obesity prevalence is rising at unprecedented levels, with current projections estimating that more than half of the world’s population will live with the chronic disease by 2035. Previous research has identified suboptimal health behaviors, particularly diet, as major contributors to obesity onset.

Eggs present an everyday, affordable, and widely consumed source of high-quality protein, nutrients, and essential amino acids. Unfortunately, eggs are rich in cholesterol (∼186 mg per large egg), a notable risk factor for obesity. While several studies have suggested that moderate egg consumption (1-2 eggs daily) does not significantly affect circulating cholesterol levels, there is considerable variability in individual responses, with some individuals metabolizing dietary cholesterol more effectively than others. The dearth of comprehensive reviews on the topic leaves clinicians, dieticians, and consumers alike unsure of the health impacts of egg-derived nutrients and their individual or supplementary obesity risks.

About the Review

The present review aimed to unravel the relationship between egg consumption (in healthy humans) and obesity incidence, focusing on the individual and summative impacts of different egg-derived nutrients, thereby informing future dietary guidelines of the pros and cons of egg consumption (including daily/weekly recommended intake guidelines). Publication screening was conducted via a custom keyword search across three online scientific literature repositories – Scopus, PubMed, and Google Scholar. These repositories were queried for relevant articles, publications, reviews, or meta-analyses between 2002 and 2022.

Identified publications were screened to eliminate duplicates, non-English publications, short communications, case reports, or publications presenting incomplete information. Subsequently, the review synthesized included publications that concisely define obesity and list its health risks, global consumption trends, current prevalence, and future projections. It then identifies and collates data on egg-derived nutrients commonly implicated in obesity research, particularly cholesterol, lecithin, fatty acids, proteins, vitamins, and minerals.

Review Findings

The review identified cholesterol as the most controversial nutrient in egg-obesity discourse but highlights that the healthy human body’s endogenous modulation of externally consumed cholesterol is more than sufficient to account for moderate egg consumption (~1-2 eggs daily). Previous research has failed to establish a concrete link between moderate egg consumption and obesity or overweight (BMI > 25). These conclusions are underscored by summary statistics, which reveal that <10 eggs per week do not significantly alter obesity risk.

In contrast, eggs are one of the healthiest sources of protein and essential amino acids, and they also contain significant vitamin and mineral quantities, underscoring their overall health benefits. “When the weekly intake is between seven and eight, people with a normal weight BMI of <25 are not at risk of being overweight or obese and are maximizing their nutrient intake,” the authors stated.

Recent research suggests that cooking methods may alter the nutrient profiles of eggs, with frying and overheating resulting in nutrient losses. Soft-boiled eggs were recommended as the most nutritious preparation method, retaining both lipids and bioactive nutrients. Undercooked egg whites, however, may present risks due to antinutrient factors and bacterial contamination. Current dietary recommendations consider boiled or soft-boiled eggs the healthiest, though additional targeted research is required to confirm these assumptions.

Conclusions

The present comprehensive review highlights the lack of evidence linking frequent but moderate egg consumption to increased obesity risk. The limited literature investigating egg cholesterol content with undesired health outcomes reveals that the human body’s endogenous cholesterol modulatory mechanisms are sufficient to account for egg-derived excess cholesterol. In contrast, eggs are one of the healthiest sources of protein, essential amino acids, and micronutrients beneficial to human health.

In summary, the health benefits of eggs make them an ideal addition to humans’ daily diets. While people with preexisting cholesterol conditions (high reactivity or high baseline values) may need to restrict their weekly egg consumption, healthy individuals should have no concerns with <10 eggs weekly. Further research is warranted to explore how cultural dietary patterns and egg consumption impact obesity risk, as eating habits differ significantly across populations. Additional research is required to identify the best cooking methodologies for optimal egg nutrient absorption.