Effect of extended morning fasting upon ad libitum lunch intake and associated metabolic and hormonal responses in obese adults

Abstract

Background/objectives: Breakfast omission is positively associated with obesity and increased risk of disease. However, little is known about the acute effects of extended morning fasting upon subsequent energy intake and associated metabolic/regulatory factors in obese adults.

Subjects/methods: In a randomised cross-over design, 24 obese men (n=8) and women (n=16) extended their overnight fast by omitting breakfast consumption or ingesting a typical carbohydrate-rich breakfast of 2183±393 kJ (521±94 kcal), before an ad libitum pasta lunch 3 h later. Blood samples were obtained throughout the day until 3 h post lunch and analysed for hormones implicated in appetite regulation, along with metabolic outcomes and subjective appetite measures.

Results: Lunch intake was unaffected by extended morning fasting (difference=218 kJ, 95% confidence interval -54 kJ, 490 kJ; P=0.1) resulting in lower total intake in the fasting trial (difference=-1964 kJ, 95% confidence interval -1645 kJ, -2281 kJ; P<0.01). Systemic concentrations of peptide tyrosine-tyrosine and leptin were lower during the afternoon following morning fasting (P⩽0.06). Plasma-acylated ghrelin concentrations were also lower following the ad libitum lunch in the fasting trial (P<0.05) but this effect was not apparent for total ghrelin (P⩾0.1). Serum insulin concentrations were greater throughout the afternoon in the fasting trial (P=0.05), with plasma glucose also greater 1 h after lunch (P<0.01). Extended morning fasting did not result in greater appetite ratings after lunch, with some tendency for lower appetite 3 h post lunch (P=0.09).

Conclusions: We demonstrate for the first time that, in obese adults, extended morning fasting does not cause compensatory intake during an ad libitum lunch nor does it increase appetite during the afternoon. Morning fasting reduced satiety hormone responses to a subsequent lunch meal but counterintuitively also reduced concentrations of the appetite-stimulating hormone-acylated ghrelin during the afternoon relative to lunch consumed after breakfast.

Figure 1

Energy intake during trials. In the morning fasting trial an asymmetric confidence interval is plotted, the negative portion of which reflects the comparison between lunches and the positive portion reflects the comparison against total intake (that is, lunch plus breakfast). An asterisk above a bar represents the comparison between the total intake in the two trials (n=24), *P<0.01.

Figure 2

Metabolic responses during trials (a) plasma glucose, (b) serum insulin, (c) plasma NEFA, (all measures n=18) where missing data is owing to insufficient blood for analysis. Values represent mean±nCI. *P ⩽0.05 versus corresponding time point in other trial. Annotations on figure represent the following, B=Breakfast period, in which participants ate a prescribed breakfast during the breakfast trial and rested during the morning fasting trial. L=Ad libitum pasta lunch.

Figure 3

Hormonal responses during trials (a) plasma-acylated ghrelin, (b) plasma total ghrelin, (c) plasma PYY, (d) serum leptin, (all measures n=18) where missing data is because of insufficient blood for analysis. Values represent mean±nCI. *P<0.05 versus corresponding time point in other trial. Annotations on figure represent the following, B=Breakfast period, in which participants ate a prescribed breakfast during the breakfast trial and rested during the morning fasting trial. L=Ad libitum pasta lunch.

Figure 4

Appetite score during trials. (n=24), values represent mean±nCI. *P<0.01 versus corresponding time point in other trial. Annotations on figure represent the following, B=Breakfast period, in which participants ate a prescribed breakfast during the breakfast trial and rested during the morning fasting trial. L=Ad libitum pasta lunch.