Eggs for breakfast: long-term (6-month) impact on body weight

The aim of the study was to investigate, over 6 months, the impact of consuming 2 eggs for breakfast on 5 days per week compared with eating cereal for breakfast on body weight, body composition, glucose and lipids and Vitamin D status. Body composition (lean and fat mass) by DEXA was measured at baseline but could not be measured at 6 months because of restrictions imposed by COVID-19.

Methods

This was a randomised parallel study of two energy restricted diets that compared consuming 2 eggs for breakfast on 5 days per week compared with eating cereal for breakfast, over a 6- month period. Both diets had a similar energy (kilojoule) content (5500kJ for women and 7000kJ for men).

Measurements

Participants attended the UniSA in the morning having fasted overnight for the measurement of weight, height and DEXA (baseline) and to have blood samples taken.  

Results

Participants

One hundred and ten participants, age 56±16 years, BMI 34±6 kg.m2, 84 women and 26 men, were randomised to commence the study.

Outcomes

Seventy-six participants completed the study, 33 in the egg group and 43 in the cereal group. Weight loss in completers was 8.1 kg (±7.0 kg) in the egg group and 7.3kg (±4.0 kg) in the cereal group. There was a significant effect of time (P<0.001) but there was no differential effect of diet (p=0.56). The egg group had 2 individuals with very large weight losses of >20kg which made the data skewed. Removal of these 2 individuals normalised the data but had no effect on the results but the egg weight loss was slightly lower at 6.7 kg (±4.6 kg). The percentage weight loss was very similar in the normalised group 7.9% eggs and 7.6% cereal. Weight loss had no effect on glucose and lipids which were all normal to begin with.

Vitamin D was normal (55±18 nmol/L) at baseline rose at 3 months and fell at 6 months but still remained higher than baseline (P<0.001 for time). There was no difference between the two groups. Vitamin D levels were inversely correlated with BMI (r=-0.22 p=0.025) and positively with age (r=0.26 p=0.009) and change in Vitamin D was positively correlated with weight change at 3 and 6 months (r=0.46 and r=0.41 both p<0.001). In a post-hoc analysis when only obese participants were included in the analysis of Vitamin D, participants on the egg diet maintained the increase in Vitamin D levels seen in both groups at 3-months. This remains to be clarified in a prospective study in obese participants only.

Overall Conclusions

Both eggs and cereal eaten for breakfast during an energy-restricted diet resulted in similar weight loss. There were no adverse effects on total and LDL cholesterol. There may be a beneficial effect on Vitamin D in people with obesity but this remains to be investigated in a prospective study.