Breakfast is the most important meal of the day. The consumption of breakfast has been identified as an important factor in nutritional well-being, contributing significantly to total daily energy and nutrient intake (Nicklas, 1993), and supporting healthy growth and development (Whitney, 2007). The majority of breakfasts consist of a variety of carbohydrate sources, including cereals, rice, fruit and vegetables. Carbohydrates are the main source of energy in most diets and average between 55% and 60% of total energy intake (Asp, 1994; Insel, et al., 2007). Their ingestion is essential for optimal brain functioning (Insel, et al., 2007), and have been shown to have considerable benefits in cognitive performance, particularly in children (Dye L, et al., 2002).
Various studies have suggested that skipping breakfast may impair problem solving skills, (Pollitt E, 1983) concentration levels (Mahoney, 2005) and effect overall academic achievement in children. (LoÂ´pez-Sobaler, 2003) Between 1965 -1991 breakfast consumption declined particularly in teenagers resulting in only 64% of adolescents consuming breakfasts (Seiga-Riz, 1998). Research has shown that children skip breakfast more than any other meal throughout the day (Savige, 2007), with female adolescents more likely to than males. Several investigations directly looking at the effect of breakfast consumption on academic performance suggested that children had an increased cognitive ability when consuming breakfast before school; particularly school breakfast clubs/programmes (Nicklas, 1998). Improvements in alertness, mood (Widenhorn-Müller K, 2008) and short term memory (Mahoney, 2005) were found, as well as a significant association with decreased absence and lateness to school (Murphy, 1998).
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Several investigators have suggested that the absence of breakfast or consumption of an inadequate breakfast may contribute to dietary inadequacies, which are rarely replenished by other meals during the day (Nicklas, 1993; Morgan et al., 1986). Ideally individual energy intakes should come from predominately three main meals, breakfast, lunch and dinner, which implies that breakfast consumers are much more likely to meet recommended intakes for vitamins and minerals than those who skip breakfast (Preziosi, 1999). It has been reported that 5-12-year-olds who regularly skipped breakfast had lower daily intakes of vitamin Bg, Fe, Ca, Mg, vitamin A, Cu and Zn compared with children who consumed breakfast cereals on a regular basis (Morgan et al., 1981). Breakfasts that include cereals have been shown to have a particularly positive effect on overall nutrient intake as most cereals are fortified with essential nutrients and supply dietary fibre (Preziosi, 1999; Williams, 2005; Smith, 2003).
Previous studies show that dietary fibre-rich foods with low energy density have a stronger effect on satiety, compared to higher energy dense foods. Isaksson et al., (2008) examined subjective appetite on 24 hr energy intake in healthy adults, after the consumption of whole grain cereal and wheat bread breakfasts. The results from the study reported significant prolonged satiety, decreased hunger and desire to eat up to 8 hours after the consumption of a low energy dense breakfast. However, there were no significant differences demonstrated on subsequent food intake.
Satiety defined as: the feeling of fullness or satisfaction during or after eating has been closely linked to the regulation of food intake. Carbohydrate ingestion has been shown to promote satiety (Anderson, 1998, 2003). The relationships between the consumption of sugars and their immediate effects on satiety and food intake have been reported in several studies (REFERENCE A FEW). Typical dietary sugars are either monosaccharides or disaccharides and include sucrose, lactose, maltose, glucose, and fructose. Studies in both humans and animals have observed fluctuations in blood glucose levels after the ingestion of sugars (Anderson, 2003 REFERNCE) Due to the simple structure of glucose; it can be converted in to energy very quickly, therefore producing a rapid and high increase in postprandial blood glucose and insulin levels. However sucrose as a disaccharide, tends to elicit less severe blood glucose and insulin levels after consumption, due to having a slightly more complex structure (Anderson, 2003, Jenkins, 1981)
The concept that glucose regulates satiety and food intake, by either increasing or decreasing blood glucose and insulin levels, forms the basis of the glucostatic theory proposed by Mayer in the early 1950's (Anderson, 2002; Grossman, 1986; Mayer J, 1953) This theory suggests that foods are only ingested when the utilisation of glucose by the various organs is insufficient (Stewart, et al., 1997).
The extent to which different carbohydrates raise blood sugar levels after eating was highlighted in the early 1970's when researchers in Europe looked at various effects that foods had on blood sugar levels (REFERENCE). The glycaemic index (GI); defined as a ranking of carbohydrates on a scale from 0 to 100, according to the extent to which they raise blood sugar levels after eating, became apparent during this time. However it was only in the early 1980's that GI was fully established, when a professor of nutrition at the University of Toronto, Dr. David Jenkins wanted to specify the types of foods that were more appropriate for people suffering from diabetes. (Wolever, 1991) His studies found that foods with a high GI increased blood sugar levels more than low GI foods over a 2-3 hour period. (Jenkins, 1987) This key finding has led to several hundred observational analyses, clinical trials and animal studies addressing this concept being published. Most report beneficial effects of a low GI diet on health benefits towards diabetes sufferers.
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Diabetes is a chronic disease that develops when the body is unable to produce enough insulin or use it effectively, therefore causing high blood glucose levels (Insel, 2007). Epidemiologic data suggests that a low GI diet plays a protective role against the development of type 1 & 2 diabetes (Nilsson et al., 2008).Furthermore, other studies have found a strong association between a high GI diet and a progressively higher risk of type 2- diabetes, in young and middle aged women (Ascherio et al., 1997; Salmeron, et al., 1997; Schulze, et al., 2004).However, the ARIC study and the Iowa Women's Health Study have reported no significant associations between high GI diets and type 1&2 diabetes, although within these studies dietary fibre was also an investigated factor (Stevens, et al., 2002; Meyer et al., 2000). Therefore, indicating that dietary fibre may have an influence on postprandial blood glucose levels (Kinmonth, et al., 1982). INLUDE about dietary fibre effects why been shown to be good for weight regulation
Several studies have indentified the positive benefits of low GI foods on blood glucose and insulin levels. In both healthy and diabetic individuals a significant difference in glycaemic response was found after the consumption of brown rice (low GI) compared to that of milled rice (higher GI). A significantly slower digestion rate and lower blood glucose response was observed after the consumption of the low GI rice (Leonara, et al., 2006). Jenkins et al., (1988), also demonstrated after a 2 week study period with non-insulin dependent diabetics, decreased fluctuations in blood glucose and insulin levels, therefore indicating the beneficial effects of a low GI diet for diabetics. This is supported by recently diagnosed diabetics being advised to consume low GI foods to help stabilise blood sugar levels and decrease risk factors of coronary heart disease (CHD) (Ebberling, et al., 2003;Fox, 2008)
The most common cause of CHD is obesity. Over the past few decades the prevalence of obesity has rapidly increased in developed countries and has raised concerns about the dietary lifestyles of both children and adults (Lobstein, 2004). The cause of this obesity epidemic has not been well defined; however increased sedentary lifestyles and changes in dietary consumption patterns have been associated with the increase (Savige, 2007). Various dietary factors including larger portion sizes (Ello-Martin, 2005), and an increased consumption of a high fat foods, are widely believed to be the major cause of obesity and excessive energy intake. RFERENCE
Dietary fat recommendations are less than 30% of daily energy intake (Insel, et al., 2007). The reduction of dietary fat is typically recommended to help aid weight loss and reduce the prevalence of obesity (AHA, 1996; ADA, 1997). However, despite decreases in dietary fat, obesity rates have risen in recent years, therefore causing controversy as to whether low fat diets are particularly effective in the prevention and treatment of obesity (Bray, et al., 1998; Willett, 1998; Astrup et al., 2000, Ludwig et al., 1999). Furthermore, observations suggest that a low carbohydrate diet is a more effective approach for body weight regulation (Speith, et al., 2000; Ludwig, 1999, 2000). Several studies have reported significantly more weight loss after a low carbohydrate diet, compared to conventional low fat diets. Individuals had greater improvements in triglyceride levels, insulin sensitivity, glycaemic control and experienced decreased feelings of hunger (Samaha, et al., 2003; Stern, et al., 2004); effects commonly associated with low GI diets (Brand-Miller, et al., 2002; Ludwig, 2000)
Foods that elicit minimal glucose fluctuations are referred to as low GI (Jenkins, 1981). Low GI diets have more recently been recommended for weight control and obesity prevention since having a greater satiety effect compared to low fat diets (Ebberling, et al., 2005) Decreased feelings of hunger prevent overeating and increased prevalence of snacking, which has been suggested to cause excessive energy consumption (Howarth, 2007).
Snacking is commonly regarded as a contributing factor in the development of childhood obesity, since children and adolescents select snacks based on taste over nutrition, and choose salty, calorific foods as snacks rather than healthier alternatives (REFERENCE). Studies have shown a direct link between satiety, obesity and high GI foods (Leathwood, 1988; Ludwig, 1999). Experimental studies involving rats after feeding on low and high GI foods, demonstrated significant physiological differences (Ma, 2005). After several weeks animals that were fed a high GI diet developed increased epididymal fat mass compared to those feeding on a low GI diet (Pawlak, 2000; Ma, 2005). Within 1 hour after consuming a high-GI meal, blood glucose levels begin to fall, causing the release of fatty acids from adipose tissue to be suppressed (Ludwig, 2002). The combination of low fatty acid concentrations and declining blood glucose levels stimulates hunger and encourages overeating, to which could potentially lead to a increased storage of body fat (Ludwig, 2007). In support of this, Speith et al., (2000) found that children consuming a low GI diet also demonstrated a significant decrease in body fat after being encouraged to eat to satiety and only snack when hungry.
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Furthermore, snacking and meal skipping have also been closely linked. It has been reported that breakfast is the most omitted meal of the day (Dubois, et al., 2009). An association between Increased snacking of high-fat foods and higher cholesterol levels were found amongst people who skipped breakfast (Resnicow, 1991; Savige et al., 2007). However, varied results have been reported, concerning breakfast consumption and effects on daily energy intake. While some studies reporting increased energy consumption, others found that those who skipped breakfast had lower daily energy intakes than individuals who consumed breakfast regularly (Hill et al. 1991; Nicklas, et al., 1993 Furthermore, breakfast skippers have been associated with higher carbohydrate intakes (Dubois, et al., 2009); suggesting that dietary carbohydrates may play a critical role in body weight regulation and that low GI diets may also be effective.
Low GI foods produce a lower glycaemic response than High GI foods. Therefore GI is a measure of the effect of carbohydrate containing foods on postprandial blood glucose levels, during a 2hr period compared with a reference standard, either white bread or glucose (Wolever, 1991). A systematic list was formed classifying carbohydrate containing foods by numerical value, Low GI <55, medium GI 56-69, and High GI 70> (Jenkins, 1981).
Despite controversial debates, glycaemic index may now be considered an important factor associated with energy intake. Previous research has been extensive, with studies demonstrating benefits of low GI diets in reducing risks of certain chronic diseases related to impairments of glucose and lipid metabolism (Henry, et al., 2009; Nilsson et al, 2008).
Various short term studies that suggest low GI meals have a higher satietogenic effect than high GI meals and help to limit subsequent food intake (Bornet, 2007; Warren et al., 2003)). At least 16 research studies published since 1977, based on GI and appetite have demonstrated beneficial effects of low GI compared with high-GI meals. Leathwood and Pollet (1988) reported lower blood glucose levels and a slower return of hunger after meals with bean puree (a low GI starch) compared with meals with potato (a high GI starch). Glycaemic and insulinemic responses to various breakfast cereals have also been reported to have an inverse relationship to satiety (Holt et al, 1992). All but one of these 16 studies demonstrated increased satiety, delayed return of hunger or decreased food intake after consuming low GI foods compared with high GI foods (Ludwig, 2000). Furthermore, significantly lower glucose concentrations have also been reported over a 24hr period, after the ingestion of a low GI beverage (REFerence).
Despite the growing evidence of the benefits of low-GI
foods for all individuals, the GI is still not widely adopted
as a dietary concept.
In spite of increasing evidence supporting the use of GI
The relationship between breakfasts and GI has been investigated increasingly over the years. A number of studies have examined the effects of low and high GI breakfast cereals; with many highlighting the benefits of low GI consumption. A study conducted by Warren et al (2003) reported that after consuming low GI breakfast cereals, preadolescent children had a significantly lower lunch intake compared to high GI cereals. This was supported by Ludwig (1999), who observed significantly lower glucose and insulin responses after ingesting a low GI meal compared with a high GI meal. However, results attained from a similar study (Henry, 2007) were found statistically insignificant, although a reduction in energy intake over a 24hr period after consuming a low GI breakfast was found.
ensuring the body has a sufficient energy (Dubois, et al., 2009) as well as affecting the regulation of food intake
Whilst the difference in energy intake following the
low-GI and high-GI breakfasts was smaller than in previous
studies, this may be due to the closer matching of dietary
fibre content of the test breakfasts. Nevertheless, these results
suggest that, at least in children, the provision of a low-GI diet
may be a dietary strategy to reduce the risk of overweight and
providing supporting evidence the benefits of consuming a low GI cereal.
Accumulating data suggest that a diet characterized by a low glycemic index (GI
Breakfast cereals in particular have been researched and there link with GI.
A number of studies have examined the relationship between low and high Gi breakfast cereals.
Many of the studies are with pre adolescent children with only ...... with adults, and generally will not fully have control of what they eat.
Further research as studies relating to this have not shown clear results in adults also incorporating satiety.
Typically low GI foods promote higher satiety or fullness, compared to high GI equivalents and are therefore followed by a decrease in energy consumption at subsequent meals throughout the day (Brand- Miller et al 2002), (Ludwig, 2000).
RELATE TO MY STUDY---------The purpose of this investigation was to test the hypothesis that consumption of high-GI foods induces a sequence of hormonal changes that lead to decreased availability of metabolic fuels, excessive hunger, and overeating in obese subjects.
Justification - age, adults other studies on children
The t-test is a parametric test which assumes that the data analyzed:
Be continuous, interval data comprising a whole population or sampled randomly from a population.
Has a normal distribution.
Sample size should not differ hugely between the groups
Therefore it is fair to say that people are not skipping breakfast intentionally, as studies have shown such significant benefits. Some research has found that a lack of time in the morning is the main factor preventing people from consuming breakfast, although others suggest that it is also that people are unaware of the importance of ingesting breakfast each day (Nicklas, 2004) or intentionally reducing their energy intake to aid weightless.
30 male and female individuals provided written informed consent to participate in the present study conducted at a sport psychology Institution in Lancashire. Approval was attained by the institutional ethics committee.
Table 1. Physical characteristics of participants at baseline (n=30), stated in Standard Deviation (SD).
Variables Mean Â± s
Age (yrs) 29 Â± 10
Weight (kg) 75.8 Â± 14.3
Height (cm) 169.9 Â± 9.6
BMI 26.0 Â± 4.1
All participants volunteered to partake in the present study and were over the age of 20 â‰¥. Volunteers who were breakfast skippers or had diabetes were excluded. Participants were informed of any risks as well as the protocol and given the opportunity to ask any questions prior to the study. Participants were able to withdraw from the study at any time without giving a reason before the analysis of the results had been carried out. Data was collected on age, weight and height in order to calculate BMI and find out participant characteristics.
Each individual participant was given eight pre packaged breakfast cereals. All were pre weighed (35g) using scales (Hanson). Four of the packaged cereals contained All-Bran (Kelloggs) and had an estimated GI of <55. The remaining four contained Cornflakes (Kellogg's) and had an estimated GI of 75>.The GI values of these cereals were estimated from the international GI tables and manufacturers' information, which provided a guide to the GI value. Participants were given two 4-day diet diaries which also included a clear example showing the correct way of completing them, and eight incomplete visual analogue scale questionnaires (VAS).
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The participants were randomly split in to two equal groups. Over a 3 week period, participants were required to consume two test breakfast cereals with differing glycaemic index. During the first week, group 1 consumed All Bran (a low GI cereal) while group 2 consumed Cornflakes (a high GI cereal) over a 4 day consecutive period. After a 7 day break, the second week of testing was carried out and followed the same procedure as the first week, but with group 2 now consuming all bran and group 1 consuming cornflakes. Participants were instructed to consume both breakfast cereals with the same measure of milk, although the option was given to choose their own preference of milk. Participants were required to wait one hour before ingesting anything else except water. Following this, a VAS questionnaire was asked to be completed, consisting of five questions; used to measure subjective feelings of appetite, thirst, fullness and level of satisfaction of the breakfast cereals provided. The VAS questionnaire consisted of a 10cm horizontal line separated at each end with opposing statements. Subjective appetite (VAS - Motivation to Eat) was assessed using four scales which measured: 1) Stomach fullness ('not at all' to 'extremely full') 3) Satisfaction ('not at all satisfying' to 'extremely satisfying') 4) Hunger ('not at all hungry' to 'extremely hungry') 5) desire to eat ('not at all strong' to 'extremely strong'). 2) Thirst was also measured ('not at all thirsty' to extremely thirsty') to find out if thirst can encourage the onset of hunger rather than hydration.
The participants were then asked to place a vertical line on the horizontal line to indicate their feeling at that point in time. Following the completion of the VAS questionnaire participants were free to consume their normal daily food consumption. A detailed food diary was asked to be completed including accurate weights, measures and brands if possible. Participants were debriefed upon the completion of the testing.
Statistical analysis was performed using SPSS (version 17.0, SPSS inc., Chicago, IL).The normality of the data was tested using the kolmogorov-Smirnov statistic before analysis. Data was presented as means and standard deviations, and was examined using a paired t-test to determine the differences in energy intakes between the low-GI and high-GI breakfast testing. Statistical significance was set at P<0Â·05. All dietary analysis of the diet diaries were undertaken using a Windiet Research software; a nutritional diet package (Univation Ltd, Robert Gordon University, Aberdeen, UK). VAS questionnaire scores were calculated by measuring the distance in millimetres from the beginning of the horizontal line to the position of the vertical line (from left to right) and averages were calculated for each question.
May want o include what statistical anayiss involved. -c ompairing energy intake for up to lunch and daily intakes.
Where do i include why i measured thirst from VAS.
Table 1. Percentage of participants obese, overweight and within a normal range.
% (n) % Female (n) % Male (n)
Obese 13 (4) 10 (3) 3 (1)
Overweight 50 (15) 30 (9) 20 (6)
Normal range 37 (11) 17 (5) 20 (6)
Effect of low GI and High GI breakfasts on subjective appetite & Satiety
Based on the mean VAS scores, All-Bran led to a greater feeling of fullness (6.6 Â±1.1) compared to the Cornflakes cereal (4.3 Â±1.3, P = <.001), as shown in figure 1. The mean VAS scores shown in Figure 2 illustrate that following the consumption of Cornflakes, there was an increased desire to eat (6.3 Â± 1.7) after one hour, while a significantly lower desire was found after the consumption of All-Bran (4.2 Â±1.7, P = <.001).
Figure 1. Mean (SD) of subjective appetite values for the Motivation to Eat VAS. 1) Stomach fullness ('not at all' to 'extremely full'). Higher values represent greater satiety.
Figure 2. Mean (SD) of subjective appetite values for the Motivation to Eat VAS. 5) Desire to eat ('not at all strong' to 'extremely strong'). Lower values represent greater satiety.
Figure 3. Mean (SD) of subjective appetite values for the Motivation to Eat VAS. 3) Satisfaction ('not at all satisfying' to 'extremely satisfying'). Higher values represent greater satiety.
Figure 4. Mean (SD) of subjective appetite values for the Motivation to Eat VAS. 4) Hunger ('not at all hungry' to 'extremely hungry'). Lower values represent greater satiety.
Figure 5. Mean (SD) of subjective thirst for the Motivation to Eat VAS. 2) Thirst ('not at all thirsty' to extremely thirsty'). Higher values represent a greater desire for liquids.
VAS satisfaction scores of both high and low GI cereals are shown in Figure 3. Cornflakes were found to be less satisfying (4.5 Â±1.4), since All-Bran (5.2 Â±1.1) had a significantly higher VAS score (P = .049). Participants were also significantly hungrier, one hour after consuming Cornflakes (5.7 Â±1.4), compared to one hour after they consumed the All-Bran cereal (4.5 Â±1.6, P = .002), as shown in figure 4. Each of the four questions measuring subjective appetite from the motivation to eat VAS were found to be significant; all indicating a greater satiety effect after the consumption of a low GI breakfast cereal such as All-Bran.
The differing Mean VAS scores for subjective thirst between the high and low GI breakfast cereals are shown in figure 5. One hour after the consumption of cornflakes (5.1 Â±1.4) there was an increased desire for liquids as participants were significantly thirstier (P = .006), than they were after consuming the All-Bran cereal (4.1 Â±2.0).
Effect of low GI and High GI breakfasts on food intake
Energy intakes prior to lunch were analysed in order to reflect the satiating effect (2-3 hrs) following the consumption of both high and low GI breakfast cereals (Figure 6). There was a significantly lower energy intake after the consumption of the All-Bran cereal; compared to an increase of 6537 kJ (1562 kcal) after consuming the Cornflakes cereal (P = < .005). The outcome of this result reflects the results of the VAS; indicating that the consumption of a low GI breakfast cereal results in decreased hunger and therefore increased satiety.
Figure 6. Mean (SD) energy intakes of the low and high GI breakfast cereals prior to lunch.
Mean daily energy intakes, following the consumption of low and high GI breakfast cereals are shown in Table 2. There was a higher energy intake after consuming the high GI breakfast (Cornflakes) compared to the low GI breakfast (All-Bran). However, the mean difference of 237kJ (56kcal) was not significant (P= .058)
Table 2. Mean daily energy intake of low GI and high GI breakfast cereals.
Low GI High GI
Mean Â± SD Mean Â± SD P
Energy (kJ) 6923 1139 7160 1203 .058
Energy (kcal) 1654 272 1710 287
State main finding of the study
The present study examined the influence of carbohydrates of varying GI on subjective appetite and food intake in healthy adult individuals