Short-Term Hunger Intensity Changes Following Ingestion of A Meal Replacement Bar for Weight Control

Abstract

Meal replacement products for weight-loss are popular and safe for most unsupervised consumers desiring to lose weight. Previously we reported that the thickness of meal replacement diet shakes had a direct and significant effect on hunger intensity during the first 2 h and that hunger intensity scores for liquid meal replacements were significantly below baseline for 3 h following consumption (Mattes, R.D.; Rothacker, D. Beverage viscosity is inversely related to postprandial hungar in humans. Physiol. Behav. 2000, 74 (4–5), 551–557.). This study uses the same protocol to investigate meal replacement bars designed for overweight consumers. Subjects were prescreened to include only those that normally ate breakfast and liked chocolate. The bar used in this study contained 250 calories (about 30 more than most liquid diet shakes) 4 g of dietary fiber, 14 g protein, and 8 g of fat. Subjects were instructed consume the entire bar with a glass of water following an overnight fast when they would normally consume their first meal of the day and to assess their hunger on a 1 (not hungry at all) to 9 (as hungry as I have ever felt) scale before consumption, immediately after and hourly for 6 h (only on typical weekdays). Similar assessments were made for the perception of stomach fullness (1 = empty, 9 = extremely full), strength of the desire to eat (1 = no desire, 9 = extremely strong) and thirst (1 = not at all thirsty, 9 = extremely thirsty). One-hundred and eight subjects (23 males; 85 females) completed the study. No gender satiety differences were found. Hunger ratings and desire to eat remained significantly below baseline for 5 h following consumption. Stomach fullness scores were significantly above baseline for 5 h. Thirst scores were significantly below baseline for 3 h. Although the meal replacement diet bars contained only 30 additional calories than liquids, they provided an additional 2 h of hunger suppression from baseline which may have an impact on overall weight loss success. These results support superior short-term hunger control with solid meal replacements.

Introduction

Satiety is logically important for success with any weight loss plan. Meal replacement products for weight loss should ideally be formulated such that a dieter is not hungry between meals. Meal replacements have become popular to aid in weight control and are available as liquid and solid (shakes and bars) meals. Physical state of foods (solid, semi-solid, and liquid) has been hypothesized to affect the intensity and duration of satiety in adults.1 2 3 4 5 6 7 8 9 The results, however, have not been consistent. Short-term satiety from preloads of varying consistency, if different, could be an important factor in the treatment of obesity and in the development of diet plans to suit individual needs. A previous study, found satiety differences in liquid meal replacements of different viscosity's.1 The thicker formula was shown to be significantly more satiating over a 4-h period than the thinner formula. The study described here involves the evaluation for weight loss potential of bar meal replacements of similar nutritional content as the diet shakes over a 6-week period and the evaluation of the bar in hunger control over a 6-h test period.

Methods

Families and individuals as listed in a telephone book of several rural villages in Marinette County (Northern WI) were invited by postcard to meet at the local Village Center. Any individual over 17 years of age without significant health problems that liked chocolate bars and after review of the ingredients found nothing that was contraindicated to their health could participate. All subjects signed informed consent forms. Subjects were offered $25.00 for their efforts. The meal replacement bars each had 250 calories, 4 g of dietary fiber, 8 g of fat, and provided 33% of the daily value of vitamins A, D, riboflavin, B6, B12, C, E, thiamin, niacin, folic acid, biotin, and pantothenic acid. Each bar also supplied 33% of the daily value of the following minerals: calcium, magnesium, iodine, chromium, molybdenum, phosphorous, and selenium and 15% of the daily value for zinc and iron. Subjects replaced 1 to 2 meals per day over the 6-week active phase and all subjects made at least two hunger assessments on typical weekdays.

The use of visual analogue scales to assess appetite has been reported.10 11 Hunger was assessed on a 1 (not hungry at all) to 9 (as hungry as I have ever felt) rating scale prior to consumption, immediately after and hourly for 6 h. Feelings of stomach fullness were assessed on a 1 (very empty) to 9 (extremely full) rating scale over the same 6 h period. Other hourly assessments included: the strength of the desire to eat measured on a 1 (no desire) to 9 (extremely strong) scale and the amount of food the subjects felt they could consume at that moment, measured on a 1 (nothing at all) to 9 (a very large amount) scale. Subjects were also asked to assess hourly how thirsty they felt (1 = not at all, to 9 = extremely thirsty). No additional food was allowed during the test period. Tests with baseline hunger scores of less than 3 were not used in the analysis, as the subjects were instructed not to proceed unless they had at least a 3 on the 1–9 hunger scale. Changes from baseline (within-group) were determined for all assessments using paired t-tests. All tests were two-tailed and all statistics were run on SPSS® 10.0 (1999) for the Macintosh.

Results

One hundred and sixty-four (164) subjects were initially enrolled in the study and 108 subjects completed the study following the protocol (85 females and 23 males). Approximately 1/3rd did not complete the study following the protocol. The mean age was 50 ± 17 and the mean BMI was 32.6 ± 7.3. Males lost an average of 5 ± 2.9 kg and females lost 3.4 ± 2.2 kg over the 6-week study period. No gender differences in hunger, fullness, desire to eat, how much one could consume and thirst ratings were found, therefore all results are combined.

The duration of the depressed perceived postmeal hunger scores below baseline were significant through 5 h (Table 1). Scores for sensation of stomach fullness (Table 2), the desire to eat (Table 3), and the perceived quantity of food subjects felt they could eat at the moment (Table 4) were consistent with the data for hunger (Tables 2, 3, 4). Thirst assessments were significantly reduced from baseline between 1–3 h following consumption of the bar with a glass of water, although the change was relatively small (Table 5).

Table 1 Mean changes in hunger scores following consumption of a meal replacement bar (1 = not at all hungry; 9 = extremely hungry) N = 108

Mean hunger score	Standard deviation	Significance over baseline
Baseline	6.0	1.6
Just after	2.6	1.9	0.001
1 h	2.4	1.7	0.001
2 h	2.9	1.8	0.001
3 h	3.7	2.1	0.001
4 h	4.7	2.2	0.001
5 h	5.4	2.2	0.023
6 h	6.1	2.2	0.349

Table 2 Mean changes in stomach fullness scores following consumption of a meal replacement bar (1 = very empty; 9 = extremely full) N = 108

Mean fullness score	Standard deviation	Significance over baseline
Baseline	3.7	1.8
Just after	6.7	2.0	0.001
1 h	6.5	2.1	0.001
2 h	5.9	1.9	0.001
3 h	5.3	1.9	0.001
4 h	4.7	2.0	0.001
5 h	4.3	2.0	0.044
6 h	3.8	2.0	0.906

Table 3 How strong is your desire to eat before and following consumption of a meal replacement bar? (1 = no desire; 9 = extremely strong desire) N = 108

Mean fullness score	Standard deviation	Significance over baseline
Baseline	6.0	1.7
Just after	2.3	1.8	0.001
1 h	2.3	1.7	0.001
2 h	2.9	1.9	0.001
3 h	3.7	2.1	0.001
4 h	4.7	2.3	0.001
5 h	5.4	2.3	0.012
6 h	6.2	2.2	0.392

Table 4 How much food do you think you can eat before and following consumption of a meal replacement bar? (1 = nothing at all; 9 = a very large amount) N = 108

Mean fullness score	Standard deviation	Significance over baseline
Baseline	5.9	1.5
Just after	2.5	1.8	0.001
1 h	2.5	1.6	0.001
2 h	3.1	1.8	0.001
3 h	3.8	1.9	0.001
4 h	4.8	2.1	0.001
5 h	5.4	2.1	0.058
6 h	5.9	2.1	0.579

Table 5 How thirsty are you right now? (1 = not at all; 9 = extremely) N = 108

Mean fullness score	Standard deviation	Significance over baseline
Baseline	6.0	2.5
Just after	5.8	2.4	0.360
1 h	5.0	2.4	0.013
2 h	5.0	2.1	0.012
3 h	5.2	2.0	0.023
4 h	5.5	2.1	0.094
5 h	5.6	2.0	0.133
6 h	5.8	2.0	0.543

Discussion

Meal replacements are good vehicles for studying satiety, as most of the macronutrients and micronutrients are controlled for. Previous studies have consistently shown liquids to be less satiating than solids; however, the meals tested differed greatly in macronutrient content.3 7 8 9 In this study, the more solid meal replacements satisfied hunger longer than did the liquid meal replacements following the same protocol.1 Hunger scores for the bar remained below baseline for 5 h compared with 3 h for liquid meal replacements. This bar meal replacement did have 30 more calories than did the other meal replacements; however, if the addition of just 30 calories allowed a gain of two added hours of satiety it may be worth it in the long run for products designed for weightloss, especially in patients that have difficulty controlling their appetite. Further, little difference in the effects of preloads containing 300 and 600 kcal on subsequent food intake have been reported.12 The bars were also higher in fat than the liquid shakes (8 g compared with 2–3 g). Fat infused intraduodenally has been shown to suppress appetite more than glucose infusions12 but results on appetite have not been consistent.5 13 14 15 16 17 18

The role of satiety in weight control has not been adequately investigated and logically impacts compliance with a weight control plan. Future studies should investigate further the role of satiety and use the information to better develop effective diet plans for weight control. If physiologic signals from similar preloads differing primarily in consistency are different, then over time this can lead to positive energy balance and resulting weight gain.

Hunger suppression and perceived stomach fullness were consistently greater for more solid preloads. These results were in agreement with others that found more solid foods to have a greater effect on hunger suppression.2 4 7 This requires further research as the information may be useful in developing diet plans and foods for weight loss as well as to provide a better understanding of appetite, the disease of obesity and its etiology.

Acknowledgments

The study owes much to the direction and advice from Dr. Richard Mattes, (Purdue University, Department of Foods and Nutrition, West Lafayette, IN) and Jane Quinn for her help editing.