The Impact of Diet Type on Weight Loss in Patients with Alzheimer’s Disease

Abstract

Objectives: To compare differences in weight loss in patients with Alzheimer’s disease on normal, diabetic, or texture-modified diets. Methods: This prospective interventional study examined the data of patients with Alzheimer’s disease who were admitted to a long-term care hospital in Japan from February to April 2013. Dietary elements and weight loss over a 3-month period were examined. Results: Of the 75 patients examined, 6 were on a normal diet, 10 were on a diabetic diet, and 59 were on a texture-modified diet. Weight loss was significantly associated with body weight, Mini Nutritional Assessment®, and diet type. In the non-malnourished patients, there was a significant difference between the three types of diets in terms of eating rate and weight loss. Conclusion: Diet type was independently associated with weight loss in patients with Alzheimer’s disease. Research using larger sample sizes is necessary to eliminate the differences between these diet types.

Keywords

Alzheimer’s disease therapeutic diet diabetic diet texture-modified diet weight loss

Highlights

1. Weight loss was significantly associated with body weight, MNA®, and diet type.

2. In non-malnourished patients, there was a significant difference among the three diet types in weight loss.

3. In malnourished patients, there was no difference between the diabetic diet and the texture-modified diet in weight loss.

Introduction

In Japan, the aging rate is the highest in the world, and as a result, the number of patients with Alzheimer’s disease is ever-increasing.^1,2 Individuals with Alzheimer’s disease frequently develop serious difficulties with eating and experience changes in eating and dietary habits.³ This often causes patients with Alzheimer’s disease to suffer from malnutrition and protein and energy loss, which lead to unintended weight loss and loss of muscle mass with functional decline and frailty.^4,5 Among patients with Alzheimer’s disease, malnutritional and functional indicators were associated with higher mortality risk, regardless of cognitive function.⁶

Weight loss in patients with Alzheimer’s disease is multifactorial, and its etiology remains unclear.⁷ Therefore, there are no established dietary indicators for energy and protein to be provided to patients with Alzheimer’s disease in Japan.⁸ A previous study showed that it is important to consume more than 30 kcal/kg of energy per body weight and 1.1 g/kg or more of protein per body weight to prevent weight loss in patients with Alzheimer’s disease; moreover, it reported that malnutrition has an impact on weight loss.⁹ Further multifaceted studies are needed to prevent weight loss in patients with Alzheimer’s disease.

Different types of normal and special diets are administered to hospitalized patients with Alzheimer’s disease in Japan.¹⁰ Normal diets are provided based on the Ministry of Health, Labor and Welfare’s “Dietary Intake Standards for Japanese People” with energy levels adjusted to the patient’s age, gender, and physical condition.¹¹ Based on the criteria of the Guidelines of the Japanese Society for Parenteral and Enteral Nutrition,^8,11 special diets for patients with Alzheimer’s disease include an energy per body weight of 20–30 kcal/kg/day and a protein per body weight of 1.0–1.2 g/kg/day for elderly patients. Moreover, different types of special diets are based on indicators set by special academic societies such as the Japan Diabetes Society.¹²

Moreover, patients with Alzheimer’s disease have trouble swallowing as the disease progresses.^13,14 Therefore, normal diets and special diets, which are then provided as texture-modified diets, are recommended according to the swallowing disorder.¹⁰ It has been reported that texture-modified diets contain lower energy content as the patients progress through the disease stages, resulting in weight loss.^15,16

Therapeutic diets for patients with Alzheimer’s disease in Japan are mainly categorized into three main types based on energy: normal, diabetic, or texture-modified diets. A normal diet generally includes an energy per body weight of 30–35 kcal/kg. A diabetic diet is an energy-restricted diet and includes an energy per body weight of 25–30 kcal/kg. The texture-modified diets are designed for dysphagia patients and provide less energy than normal diets. Oral nutrition supplements are supplied to the patients to compensate for these deficiencies.¹⁵

Thus, the therapeutic diets supplied to patients with Alzheimer’s disease may have different effects on weight loss because the amount of energy provided by each type of diet is different. However, no study has examined the differences in weight loss in patients with Alzheimer’s disease on normal, diabetic, or texture-modified diets in Japan. Therefore, this study examined whether these types of diets were associated with weight loss in patients with Alzheimer’s disease over a three-month period.

Methods

Study Patients

This prospective interventional study examined data of patients with Alzheimer’s disease who were admitted to a long-term care hospital from February to April 2013. This study used the data retrieved from a previous interventional study, which aimed to determine the threshold of daily energy and protein requirements to prevent weight loss in patients with Alzheimer’s disease.⁹ Psychiatrists recruited patients with a diagnosis of probable Alzheimer’s disease according to the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition,¹⁷ to participate in the study. Exclusion criteria were as follows: patients with different types of neurological disorders other than Alzheimer’s disease; patients with tenderness, impaired renal, hepatic, or cardiac function; and patients with an active inflammatory response based on serum C-reactive protein >.06 mg/dL.

Eighty-two patients who were consuming a hospital diet as their sole source of nutrition were recruited for the study.^9,10 Patients who subsequently received intravenous fluids or artificial nutrition, those hospitalized, or those who had a change in dietary status were excluded from the study. The remaining 75 patients were included in this study. The method and duration of texture-modified diet administration varied depending on the patient chewing and swallowing status on admission. This study was approved by the Ethics Committee of Mitate Hospital (2012.12). Written informed consent was obtained from the patients’ families.

Physical and Biochemical Parameters

Physical measurements were performed on the first day of the study; body height and weight were measured, and body mass index (BMI) was determined. Ideal body weight (IBW) was calculated by multiplying BMI 22 kg/m² by the square of the height. After the 3-month study, body weight was remeasured, and weight loss was calculated by subtracting the body weight at 3 months from the body weight measurement taken on the first day. Clinical psychologists used the Mini-Mental State Examination¹⁸ to assess cognitive function. It is a 30-point scale, with lower scores indicating severe cognitive impairment. According to the score, patients with a score ≤21 were strongly suspected of having dementia, those with a score between 22 and 26 were suspected of having mild dementia, and those with a score between 27 and 30 were considered to have intact cognition. The Barthel Index¹⁹ was used to evaluate activities of daily living by occupational therapists. According to the score, patients with a score ≤40 required overall assistance, those with a score between 45 and 55 required moderate assistance, and those with a score ≥2460 were moderately independent. The MNA® (Mini Nutritional Assessment)²⁰ was used by charge nurses to assess the nutritional status of patients. According to the score, patients with a score <17 were considered to have malnutrition, those with a score between 17 and 23.5 were suspected of having malnutrition, and those with a score between 24 and 30 were considered to have an adequate nutritional status.²¹ All parameters were measured at the end of the study.

Nutritional Intervention

This interventional study examined the association between diet and weight loss over a 3-month period in patients with Alzheimer’s disease. Methodological details have been described elsewhere.^9,10 Briefly, the study period was 21 days, consisting of 7 consecutive days in each month.

The eating rate was calculated by measuring the actual meal intake of each patient. A detailed method has been described elsewhere.¹⁰ The measurement of meal intake was performed at every meal by 5 registered dietitians. First, the standard serving size of each prepared meal was weighed with a digital scale, and the weight was registered as the standard initial weight (A & D Company, Limited, Tokyo, Japan; max. capacity: 3000 g, resolution: .1 g). Next, the weight of each leftover meal was measured, and the eating rate was calculated by subtracting the weight of the leftover meal from the weight of the prepared meal.

The amount of energy and protein consumed by each patient was calculated as follows. First, the energy and protein provided by each meal were multiplied by the eating rate of each patient. Then, the energy and protein consumed of all the meals eaten by the patients in a day were summed. The average of the energy and protein consumed for the 21 days was then calculated.¹⁰ To standardize and evaluate energy and protein intake, we calculated energy and protein intake per kilogram according to the body weight of each patient.

Classification of Types of Diets

The patients’ doctors recommended diet types based on the patients’ chewing or swallowing capabilities, and types of diets comprised nine therapeutic diets, one normal diet, and eight disease-specific (eg, diabetes mellitus, heart disease, and dyslipidemia).¹⁰ Regarding the needed amounts of energy and protein for the diets, the doctors considered each patient’s active and stress factors.⁸ The amount of energy was restricted in diabetic diets to keep the patient's blood glucose level.¹² The types of diets were approximately divided according to the amount of energy provided in the following three categories: normal diet, diabetic diet, or texture-modified diet.

1. Normal diet: for patients with no chewing or swallowing difficulties;

a. Energy provided: 30–35 kcal/body weight

b. Protein provided: 1.0–1.2 kcal/body weight

2. Diabetic diet: for patients with diabetes mellitus;

a. Energy provided: 25–30 kcal/body weight

3. Text-modified diet, with chewing or swallowing difficulties;

a. Energy provided: 25–35 kcal/body weight

b. Protein provided: .8–1.2 kcal/body weight

4. Soft foods: for patients with mild chewing or swallowing difficulties;

5. Porridge and side dishes: for patients with moderate chewing or swallowing difficulties;

6. Liquidized food: for patients with severe chewing or swallowing difficulty; and

7. Jellied food: for patients with moderate to severe chewing or swallowing difficulties, with a low tolerance for liquidized foods.

The body weight used in the calculation was actual body weight or IBW. The food service at this hospital used a system that provides a different amount of energy for every 200 kcal of meals per day. For this reason, patients were usually provided with a little less or more energy than the determined amount of energy. The energy and protein of other disease-specific diets were in the range of the texture-modified diet. The protein range of .8–1.0 was for the kidney disease diet. Because of its low energy density, texture-modified diets provided less energy and protein than normal diets. Moreover, half-meals (half the normal diet) were also provided if the patient could not eat enough. Oral nutrition supplementations (normally, 200 kcal per bottle) were supplied to the patients in addition to normal meals to compensate for these deficiencies.¹⁰ In this study, these were included in the calculation.

The number and percentage of patients with Alzheimer’s disease according to diet type were as follows: normal, 7 (9.3%); soft foods, 14 (18.7%); porridge and side dishes, 30 (40.0%); liquidized food, 21 (28.0%); and jellied food, 3 (4.0%). The diabetic diet was as follows: normal, 1 (10.0%); soft foods, 3 (30.0%); porridge and side dishes, 2 (20.0%); and liquidized food, 4 (40.0%). The breakdown of diet types supplied to patients with Alzheimer’s disease was as follows: normal diet, 6; diabetic diet, 10; and texture-modified diet, 59.

Power Analysis

Post hoc analysis was used to calculate the power of this study with a sample size of 75 individuals. When the effect size was set to .4 and α was set nominally at .05 and β at .2 (power = .8), then the post hoc power was calculated to be .867.

Statistical Analysis

Physical, biochemical, and nutritional parameters of patients with Alzheimer’s disease were shown for each of the three diet types. Continuous data were presented as mean and standard deviation and were analyzed using the Kruskal–Wallis test. Significance values were adjusted using the Bonferroni correction for multiple tests. Categorical variables were presented as frequencies (percentages) and analyzed using the chi-squared test. A multivariable linear regression model was used to determine the association between multiple potential factors, including diet type and weight loss. Subsequently, the patients were divided into two groups according to a MNA® score of 17, which was the cut-off point for weight loss in the previous study.⁹ Furthermore, eating rate and weight loss among the three diet types are shown in a box-and-whisker diagram and analyzed using the Mann–Whitney U test or Kruskal–Wallis test. All P-values were two-sided, with .05 as the threshold for significance. All statistical analyses were performed using the SPSS 27.0 version for Windows (IBM SPSS Statistics for Windows, Version 27.0; IBM Corp, Armonk, NY).

Results

In total, 75 of the 82 patients with probable Alzheimer’s disease were analyzed. There were 6 patients on a normal diet, 10 patients on a diabetic diet, and 59 patients on a texture-modified diet. Table 1 shows the characteristics of the study patients. The mean patient age was 83.7 ± 7.2 years, and 70.7% of the patients were women. No one in the normal meal group received any meal assistance, while 42% of the texture-modified diet group received meal assistance. For Mini-Mental State Examination, the number of patients below 5 exceeded 50%, so the chi-square test could not be performed. However, the texture-modified diet group had the highest percentage at 90%. Body weight (P = .045), BMI (P = .044), and Barthel Index (P = .024) were significantly lower in the texture-modified diet group than in the normal diet group. The diabetic diet group had the highest eating rate (94.7%), followed by the texture-modified diet group (89.1%) and the normal diet group (77.1%) (P = .018). The average amount of energy provided per body weight was over 30 kcal for all three types of diets. However, the average amount of energy consumed per body weight was below 30 kcal/kg for the normal and diabetic diets. The average amount of protein per body weight supplied and consumed was greater than 1.0 g/kg for all three types of diets. There was a significant difference in weight loss at 3 months, with the normal diet group exhibiting the highest weight loss, followed by the diabetic diet group (P = .049).

Table 1.

Baseline Characteristics of Patients with Alzheimer’s Disease According to Three Diet Types.^a

	Normal Diet (n = 6)	Diabetic Diet (n = 10)	Texture-Modified Diet (n = 59)	P ^b	P ^c	P ^d
Age, years, mean (SD)	82.0 (4.9)	83.6 (9.1)	83.8 (7.1)
Sex, n (males/females)	1/6	6/4	14/44
Length of disease duration, years, mean (SD)	6.5 (2.9)	6.4 (3.6)	5.5 (3.6)
Length of stay, years, mean (SD)	1.5 (1.5)	2.1 (2.1)	1.8 (1.4)
Height, cm, mean (SD)	149.4 (.1)	151.2 (.1)	149.1 (.1)
Body weight, kg, mean (SD)	51.2 (11.2)	46.5 (10.6)	41.1 (8.4)	.045		.049
BMI, kg/m², mean (SD)	22.2 (3.6)	18.9 (3.0)	18.1 (3.0)	.044		.029
Serum albumin, g/dL, mean (SD)	3.5 (.5)	3.6 (.3)	3.4 (.4)
Meal assistance, n (%)	0 (.0)	2 (20.0)	25 (42.4)
Mini-Mental State Examination score, mean (SD)	14.7 (8.2)	14.9 (7.4)	10.2 (7.5)
Dementia, n (%)	5 (83.3)	8 (80.0)	53 (89.8)
Mild dementia, n (%)	—	2 (20.0)	6 (10.2)
No cognitive deficits, n (%)	1 (16.7)	—	—
Barthel Index score, mean (SD)	58.3 (23.4)	38.0 (28.1)	28.6 (25.6)	.024^e		.015^e
Total dependency, n (%)	1 (16.7)	4 (40.0)	30 (50.8)
Severe dependency, n (%)	1 (16.7)	4 (40.0)	20 (33.9)
Moderate dependency, n (%)	4 (66.7)	—	9 (15.3)
Mini Nutrition Assessment score, mean (SD)	22.6 (4.5)	20.1 (4.5)	19.1 (3.9)
Malnutrition, n (%)	0 (.0)	3 (30.0)	16 (27.1)
At risk of undernourished, n (%)	4 (66.7)	3 (30.0)	35 (59.3)
Undernourished, n (%)	2 (33.3)	4 (40.0)	8 (13.6)
Eating rate (%)	77.1 (8.6)	94.7 (6.0)	89.1 (14.1)	.018	.019	.030
Amount of energy provided (kcal), mean (SD)	1865 (76)	1450 (80)	1515 (304)	<.001	<.001	.030
Energy/IBW, kcal/kg, mean (SD)	38.6 (14.8)	33.1 (6.5)	32.2 (5.0)	.007	.005
Amount of energy consumed (kcal), mean (SD)	1440 (196)	1256 (215)	1284 (336)
Energy/IBW, kcal/kg, mean (SD)	29.0 (.5)	27.2 (5.9)	31.9 (7.9)
Amount of protein provided, g, mean (SD)	67.7 (4.1)	56.4 (3.4)	57.1 (10.1)	<.001	<.001	.006
Protein/IBW, g/kg, mean (SD)	1.4 (.5)	1.3 (.3)	1.5 (.5)	.035	.029
Amount of protein consumed, g, mean (SD)	50.5 (6.6)	49.3 (8.8)	48.9 (11.5)
Protein/IBW, g/kg, mean (SD)	1.0 (.2)	1.1 (.2)	1.2 (.3)
Weight loss in 3 months, kg, mean (SD)	3.5 (3.8)	2.8 (3.4)	.8 (2.7)
Weight loss in 3 months, %, mean (SD)	6.8 (7.2)	5.6 (5.9)	1.6 (6.0)	.049

IBW, ideal body weight.

^aP values were adjusted for Bonferroni method.

^bStatistically significant differences between normal food, diabetic food, and texture-modified diet.

^cStatistically significant differences between normal food and diabetic food.

^dStatistically significant differences between normal food and texture-modified diet.

^eP values were calculated using the Kruskal-Wallis test.

Multivariable linear regression analysis revealed that weight loss was significantly associated with body weight (P < .001), MNA®(P < .001), and types of diets (P = .024) (Table 2). Patients were divided into two groups to eliminate the effects of malnutrition: those with the MNA® score <17 (malnourished group) and those with the MNA® ≥17 (non-malnourished group). Eating rates and weight loss were compared among the three diet types. Box-and-whisker plots of eating rates and weight loss are shown for each of the three types of diets in Figures 1 and 2. In the non-malnourished subset, there was a significant difference in eating rate (P = .041) and weight loss (P = .019) among the three types of diets. The normal diet group had the highest rate of weight loss, followed by the diabetic diet group. In the texture-modified diet group, the non-malnourished group had a median weight loss of zero, and the malnourished group had significantly higher weight loss than that of the non-malnourished group (P = .008), even though there was no difference in the eating rate.

Table 2.

Multiple Linear Regression Analysis for Weight Loss (%) of Patients with Alzheimer’s Diseases.

Predictor Variable	Unstandardized Coefficients		Standardized Coefficients
Predictor Variable	B	Standard Error	Beta	t	Significance
Age, years	−.06	.09	−.07	−.38	.499
Sex (males/females)	1.17	1.42	.09	.82	.414
Body weight, kg	.31	.08	.46	3.92	<.001
Mini-mental State Examination score	.11	.08	.13	3.92	.321
Barthel Index score	.05	.11	.19	1.00	.173
Mini Nutrition Assessment score	−1.06	.19	−.71	1.38	<.001
Amount of energy consumed (/1000 kcal)	−2.08	2.90	−.08	−5.67	.475
Three types of diets	−2.29	.99	−.22	−2.31	.024
Adjusted R² = .433

BMI, body mass index.

Figure 1.

Box-and-whisker plot of eating rates by three types of diets, according to patients with MNA Score <17 and patients with MNA score ≥17. MNA, mini nutritional assessment.

Figure 2.

Box-and-whisker plot of weight loss by three types of diets, according to patients with MNA Score <17 and patients with MNA score ≥17. MNA, mini nutritional assessment.

Discussion

This study was a prospective interventional study conducted over a 3-month period that examined the association between types of diet and weight loss in Alzheimer’s disease patients. Based on the study findings, weight loss was independently associated with types of diets, MNA® score, and body weight after adjusting for confounding factors. For the non-malnourished group, there was a significant difference in the association between types of diets and weight loss. Moreover, in the texture-modified diet group, the malnourished group had a significantly higher weight than the non-malnourished group.

Considering the different types of diets, the normal diet group exhibited the highest weight loss of the three types of diets because of their low eating rate, despite being supplied with high energy and protein. A previous study²² has reported that dysphagia could be seen in every stage of Alzheimer’s disease, that patients and caregivers may not be aware of dysphagia, and that all patients should be screened for dysphagia in every stage. The choice of an appropriate diet type is very important for patients with dementia.²³ One study reported that patients with dysphasia were likely to obtain a better eating rate with the texture-modified diet than with a normal diet.²⁴ The normal meal group had not taken a screening test for dysphagia; therefore, an undetected swallowing disorder might have made it difficult to consume a sufficient diet.

In addition to the presence of signs of dysphagia and the severity of dementia, a clinical study in Japan has shown that difficulty in initiating meals is a factor preventing meal independence in patients with Alzheimer’s disease.²⁵ Moreover, patients with Alzheimer’s disease are reported to develop an olfactory disorder from an early stage.²⁶ The normal meal group in this study had not received any meal assistance. This may be another reason for the lower eating rate in this group.

The patients supplied with the diabetic diet exhibited the highest eating rate; however, their weight loss was the second highest due to a restricted diet supply. Hospitals in Japan usually provide patients with a diet that is restricted in energy. However, Japan's cross-sectional observational study revealed that total energy expenditure was comparable between Japanese patients with and without diabetes mellitus using the doubly labeled water method and physical activity level.²⁷ Conversely, one clinical study reported that consuming vegetables and meat followed by carbohydrates can prevent postprandial excursions of glucose and insulin levels.²⁸ To prevent weight loss in patients with diabetes, a non-restrictive energy diet that incorporates ways of eating against postprandial excursions of glucose and insulin levels is necessary.

In the texture-modified diet group, weight loss did not occur when patients’ nutritional status was good. At this hospital, the dietitians provided appropriate meals according to the patients’ eating and swallowing conditions. Moreover, when the amount of diet was low, oral nutritional supplements were provided to patients to cover the lack of energy and nutrients. Furthermore, 40% of these patients were receiving meal assistance. For these reasons, it could be stated that patients do not lose weight if their nutritional status is good and they have the required amount of energy.

Conversely, weight loss occurred when patients were malnourished, despite having an adequate eating rate. Moreover, the activities of daily living of these patients were very low. Simizu et al reported that patients who had consumed texture-modified diets showed decreased skeletal muscle mass.²⁹ Meyer et al reported that malnutrition and sarcopenia exist in parallel with reduced nutrient intake, inflammation, and weight loss, as well as muscle mass.³⁰ These days, the need for a nutritional strategy that optimizes nutrition and focuses on muscle mass and weight gain has been discussed.³¹ When focusing on increasing muscle mass, the patient needs to have more energy in the meals provided in order to gain weight.

Furthermore, a certain number of patients on the texture-modified diet had severe weight loss. This suggests that the texture-modified diet may have resulted in insufficient dietary intake and weight loss. A review reported that abnormal eating behaviors, eating disorders, and dietary changes are found in most people with dementia, especially in its later stages.³² A recent observational study showed that texture-modified diets are associated with poor appetite in older adults in a post-acute rehabilitation hospital,³³ common among older adults. Moreover, an observational study in community-dwelling older people reported that reduced saliva flow rate was associated with poor dietary intake.³⁴ Many management options are available for dysphagia to address these issues, including texture-modified diets, swallowing therapy programs, non-oral feeding, medications, and physical stimulation.^35-38 Effective management of patients with a low eating rate on texture-modified diets is required.

This study had several limitations. First, the study sample size was relatively small, thus reducing the power of the study and increasing the margin of error. Second, this study was a single-center trial conducted in a long-term nursing care hospital. Therefore, it would seem hard to argue that external validity is obvious from this study. Third, although multivariate analysis of weight loss was performed and included multiple factors, other potential factors may not have been examined. Finally, patients’ conditions in the three diet groups should have been matched; however, because this study was conducted on hospitalized patients, patients’ conditions were not matched. Therefore, there was a possible selection bias in this study. In the future, this issue should be investigated in a multicenter study with a large sample size of patients with matching conditions.

One strength of this study was the measurement of plate waste as a means of calculating the amount of energy and protein consumed. This requires considerable time and effort. Using this method, we were able to calculate the eating rate as well as the amount of energy and protein consumed with high accuracy.

In conclusion, types of diets were independently associated with weight loss in patients with Alzheimer’s disease. However, there may be other confounding factors that were not adjusted for. Therefore, more studies are necessary to investigate causality using multicenter research data with larger sample size.

Footnotes

Acknowledgments

I would like to thank all the study patients, nursing staff, and dietitians. I also thank Masakatu Yoshida, MD, Yoshiaki Honda, MD for their assistance in this research, and Nobuko Amano, R. D for her nutritional data collection. I want to thank Editage () for English language editing.

Declaration of Conflicting Interests

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Tomiyo Nakamura

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