Start the Day with Protein and Fibre To Reduce Risk of Obesity

Breakfast is often stated as being the 'most important meal of the day' yet there is little evidence based advice regarding optimum foods to consume. A recent study conducted by Kranz et al. indicated that post-breakfast fullness within children is not influenced by breakfast type, yet consuming high protein and high fibre breakfasts may result in improved diet quality [1]. From reviewing these conclusions in the context of the wider literature, expanding research to all age groups, it has been found that eating breakfast regularly may help individuals to make healthier dietary choices, and that including a source of protein and fibre may reduce rise of obesity and its comorbidities.

Research has frequently associated breakfast consumption with reduced obesity [2]. Aside from alleviating the effects of the overnight fast, providing energy to undertake daily tasks and enhancing cognitive function by providing glucose for the brain [3], breakfast is believed to have a satiating effect that decreases hunger throughout the day [4]. For these reasons it is advised that 15-25% of daily energy intake should be at this meal [5]. 

In the UK 36% of adults are overweight and 27% are obese [6]. Obesity has significant implications on an individual’s short term physical and mental well-being, but is also a major risk factor for many non-communicable diseases. More specifically, visceral obesity is the most prevalent cause of the metabolic syndrome, which is linked to increased risk of coronary heart disease, stroke and diabetes as a result of chronic inflammation and insulin resistance [7].

Prevention of obesity relies on weight maintenance, which is achieved by obtaining a balance between energy input and output. Although many factors affect food consumption, hunger and satiety are the main physiological influences; these feelings are mediated by endocrine signals released by the gut and detected by the hypothalamus, the central region for appetite control [8]. Post-prandial satiety is associated with an increase in the concentration of the anorexigenic hormones glucagon-like peptide 1 (GLP-1), cholecystokinin (CCK), peptide YY (PYY), pancreatic polypeptide (PP) and oxyntomodulin (OXM), and a corresponding decrease in the concentration of the orexigenic hormone ghrelin [9].  

The relative satiating effect of different macronutrients is often discussed, with satiety from protein being thought to be sustained for longer than that from fat or carbohydrates [10]. The causative mechanism for this remains uncertain, however it is not believed to be mediated by ghrelin suppression [9]. Instead it may be attributed to a sustained CCK [11] and higher PYY response [12]. Similarly, high fibre induces a feeling of satiety as a result of slowed gastric emptying and increased gastric distention [13], as well as the colonic fermentation inducing the release of GLP-1 [14]. For these reasons weight loss diets often promote regular intake of such nutrients.  

There is vast evidence supporting general breakfast consumption, however studies specifying breakfast composition are more limited in number. A recent randomised intervention trial conducted by Kranz et al. investigated this in relation to satiety, food intake at subsequent meals and total dietary quality [1], all of which are indicators of obesity risk. This review will discuss their findings, which focus on the pre-school age group, and relate them to research within other demographics, assessing the implications on dietary advice for the general population.

Method

Study population

41 children attending 2 preschools were enrolled to the intervention.

Study design

Three energy matched (300kcal ±25kcal) breakfasts were compared to a control, the usual breakfast. The intervention breakfasts were high fibre (HF) (10g fibre/day), high protein (HP) (20g protein/day) and high protein high fibre (HPHF) (20g protein/day and 10g fibre/day). Fibre and protein content was ≥1.5 times average protein or fibre in the control and adhered to the Child and Adult Care Food Guidelines. All intervention breakfasts were lower in fat than the control. Foods were tested for acceptability by pre-schoolers before the study and modified as necessary.

Subjects were split into four groups and order of type of breakfast randomised.  Each group consumed each breakfast type for 1 preschool week, Monday to Thursday, with a 1 week wash out period in between.

Food intake, anthropometric and fullness measurements

Pre- and post-breakfast, and pre-lunch fullness was assessed on all four days of intervention each week. Food consumption during preschool breakfast, lunch and snack times was estimated on the Wednesday of each of the study weeks by direct observation. Anthropometric measurements were taken at baseline, week 3 and 7.

Statistical analysis

Fullness ratings were coded from 1 to 4, based on being ‘very empty’ to ‘very full’. Energy, food group and nutrient intakes were calculated. Diet quality was analysed using the Revised Children’s Diet Quality Index (RC-DQI), adjusted to reflect two-thirds of the daily intake recommendation. The association between breakfast type and energy intake at lunch, diet quality and fullness were statistically analysed.

Results

Results of statistical analysis

Total energy and fat intake were lower during the intervention breakfasts. Protein density (g/100kcal) was higher from the HP and HPHF than the control yet protein intake did not differ. Fibre density was higher from all intervention breakfasts. Mean carbohydrate intake was lower in HP and HPHF diets compared to control.

Breakfast type did not affect post-breakfast or pre-lunch fullness. Breakfast and lunch energy intake varied between the control and intervention breakfasts, yet snack and total daily energy intake did not. Lunch compensated for reduced energy intake at breakfast.

Adjusted diet quality scores showed differences in added sugar, fat, n-3 fatty acids and wholegrains. Highest diet quality scores were during the HP and HF interventions.

Discussion

In the study by Kranz et al. consumption of the intervention meals resulted in reduced energy intake at breakfast [1], suggesting greater satiation in response to higher intakes of protein and/or fibre, although this effect may have been altered by neophobia as a consequence of the lack of an acclimatisation period. There was no significant difference in fullness post-breakfast or pre-lunch between breakfast types, a result contrasted by Touyarous et al. who reported  hunger to be lower throughout the morning following consumption of a HF bread for breakfast compared to a control [15]. Moreover, Leidy et al. suggested that HP breakfasts cause increased feelings of fullness due to the observed reduction in ghrelin and increase in PYY concentrations [4]. It has also been shown that HP diets result in a lower glucose response than high carbohydrate (CHO) [17], which may prolong the feelings of satiety similar to that from low glycaemic index (GI) foods, which are also often HF. This suggests benefits of selecting HP and HF breakfast items in body weight management and treatment of type 2 diabetes. However, the corresponding suppressed insulin level may counteract appetite suppression due to the anorexigenic effect of the hormone [18]. It has also been suggested that animal protein has a lower postprandial glucose response than plant protein [19] making the choice of protein equally as significant.

The variation in conclusions within the literature may result from the differing characteristics of the subjects. This is of particular importance when comparing them to the study by Kranz et al. as few studies have looked into the effect of nutrients and fullness within preschool children due to the complexity of conducting research and the difficulties encountered when assessing hunger level. Moreover, 16% of boys and 32% of girls in the study were overweight or obese and it is suggested that satiety response is lower within obese children [16], potentially attenuating the effect of the intervention breakfasts.

Despite there being no difference between fullness ratings, energy compensation at lunch was observed so that total daily energy intake was the same regardless of breakfast type [1]. These findings are not consistent with wider research. It was found by Schusdziarra et al. that there is no under-consumption during the day in response to high energy intake at breakfast [20], therefore a lower energy breakfast could be associated with total reduced energy intake. Additionally, HF breakfasts have been related to reduced energy intake throughout the day [14] and Touyarou et al. concluded that breakfast GI, which may be able to be linked to fibre content, had no effect on short-term energy intake [21]. HP breakfasts have also been shown to relate to lower food intake at lunch [15], and similarly, egg consumption at breakfast has been associated with reduced daily energy intake at other meals when compared to cereal foods [22]. Again, these differences could be attributed to the variation in age group as Kranz et al. suggested that breakfast has a unique role in food intake control in children [1]. Despite this it has been shown that there is no difference in short term food intake regulation or judgement in requirements for energy compensation between age groups [23]. The childcare environment may have therefore socially facilitated eating, increasing intake [24].

Leidy found dietary quality of individuals that eat breakfast to be better than those who do not [25], with healthier food choices being made due to decreased neural activations related to food motivation and reward [23]. The improved diet quality was characterised by higher consumption of fruit and vegetables, milk, wholegrains, vitamins, minerals and fibre, and lower fat and cholesterol [25]. The inverse association between healthy eating index score and visceral obesity observed by Yoshida et al. [26] makes the findings by Kranz et al. and Leidy significant to the prevention of chronic disease as visceral obesity increases risk of the metabolic syndrome. In general, studies focus on frequency of breakfast consumption rather than type of foods consumed, however Kranz et al. observed HP and HF breakfasts to lead to an improved diet quality score compared to the control [1]. However, this result is limited by only food intake at pre-school being measured and the subsequent adjustment of RC-DQI to reflect only 66% of the day.

The mean protein and fibre intake did not vary based on breakfast type, but protein and fibre density were increased in all three intervention meals [1]. This suggests that, even if breakfast type is not correlated with improved diet quality score, regular inclusion of such foods at breakfast may help contribute to daily protein and fibre requirements.

Impacts

After considering the conclusions from the study by Kranz et al. and contrasting them with those in the wider literature it could be stated that regular breakfast consumption may support body weight maintenance due to suppressed hunger, and could offer reductions in risk of obesity and comorbidities such as CVD, type 2 diabetes, cancer and osteoarthritis [27]. Moreover, although it could be argued that not consuming breakfast may result in a lower total daily energy intake as one meal is missed [28], the improvements in dietary quality following breakfast consumption is likely to be beneficial when considering intake of individual nutrients, particularly consumption of fat and cholesterol, which contribute to visceral obesity and are significant in the aetiology of CVD. As a result, breakfast should be considered as the ‘most important meal of the day’.

Although Kranz et al. observed no link between breakfast type and appetite in pre-school children, expanding research to a more diverse age group found associations between appetite and both HP and HF breakfasts, as well as reduced food consumption at subsequent meals [20]. In addition, reduced post-prandial glucose response following HP breakfasts, which would be further enhanced by iso-calorically replacing CHO, suggests further benefits of HP and HF breakfasts for management of blood glucose level in type 2 diabetes.

Overall, the practical advice would be to ensure breakfast is regularly consumed and is a balanced meal containing a portion of protein such as milk, eggs, lean meat or fish, alongside a source of fibre like wholegrain cereal, oats or wholewheat. The evidence suggests that such meals may be effective in controlling daily energy intake and preventing weight gain in the general population.

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