Weight gain and adiposity are the two single most important causes of metabolic syndrome, type 2 diabetes mellitus, arterial hypertension, osteoarthritis, and certain cancers and represent one of the main global public health problems [
Recently, popular diets low in carbohydrates (LC) and very low carbohydrate- (VLC-) ketogenic diets, high in animal-based protein, were shown to result in weight reduction and modification of some cardiovascular risk factors [
An additional strategy for diets optimized towards weight control and optimal long-term health may involve the use of meal replacements. Previous studies with caloric restriction have shown that, by supplementing 2 out of 3 conventional meals with a meal replacement, a larger weight reduction and a better compliance with diet plan could be achieved compared to isocaloric conventional diets [
In the present study we report the effects of an ad libitum consumed plant-based diet involving 3 meals combined with 2 additional (plant-based) meal replacements on the body composition of free-living participants. We hypothesized that the application of an ad libitum low-fat plant-based diet without a prespecified calorie restriction would induce clinically relevant weight loss, predominantly via reduction of fat mass with minimal changes of fat-free mass. The impact of low-fat plant-based diets supplemented with meal replacements on body composition was so far understudied and our report reveals novel insights into the potential of this dietary approach to enable body fat reduction and muscle mass preservation.
This study was designed as an open-label, nonrandomized, controlled interventional trial, followed by a postintervention survey in a nonresident diet-optimizing program. The primary outcome of the study was a change in body fat mass, which is in agreement with recent considerations of measuring outcomes in weight intervention studies [
Baseline evaluation included a questionnaire-based survey of dietary habits, physical activity, comorbid diseases, and personal goals associated with participation in the diet-optimizing program. A questionnaire developed by the investigators was used whereby dietary habits were assessed with items defining current intake of main food groups, a typical daily meal plan, dietary supplements, and diet related health issues. Physical activity was assessed with three items in the questionnaire defining the number of exercise units per week, the type of exercise, and the time spent. Body composition was assessed at baseline, once weekly at regular follow-up meetings, and at the end of the 10-week program by an 8-electrode bioimpedance body composition monitor (Tanita BC-601F; Tanita Corporation, Tokyo, Japan). Body composition assessment measurements included body weight, BMI, body fat mass percentage relative to total body mass, visceral fat area (in arbitrary units associated with abdominal visceral fat cross-sectional area (each unit equates to 10 cm2 of visceral fat)), muscle mass, total body water, mineral bone mass, and estimated basal metabolic rate.
The initial questionnaire survey revealed that at baseline participants ingested on average 2–4 meals reflective of a typical Western-type diet: most meals were composed of animal-source nutrients (cow-milk, yoghurt, cheese, cottage-cheese, meat from various sources, eggs, and fish) and refined wheat flour based nutrients (bread, pasta, and pastry). Food preparation included various vegetable oils and fats. Unrefined and whole plant nutrients were largely absent from most meals and a minority of meals included portions of fruit and vegetables. These data indicate that our participants were in general without any significant personal preference towards plant-based diets before study entry. No ideological or philosophical arguments towards vegetarian diet choices or against animal use were mentioned.
The dietary intervention was executed in free-living conditions with participants engaging in their regular daily work and social activities. The plant-based dietary plan included 3 conventional meals based on starch nutrients (potatoes, sweet potatoes, rice, oatmeal, whole-grain pasta, beans, peas, lentils, and similar ones), fruits (seasonal fruits and various berries), and nonstarch vegetables (color and leafy vegetables). Spices and tomato sauce (without oil) and one regular-sized spoon of flaxseed were recommended as well. The participants were recommended to consume no more than 5-6 grams of salt per day. All milk and dairy products, vegetable oils, and fats were excluded from the diet. Meat was allowed (but not recommended) once weekly to relieve social pressures on participants which they often encountered from their circle of influence (i.e., family, friends, and coworkers) when changing the diet to plant-based sources. The total macronutrient composition of the intervention diet was approximated to 15% protein, 70% carbohydrates, and 15% fat. Dietary fiber content was approximated to 40–45 g per day, which is in alignment with research on plant-based dieters [
Composition of the intervention diet.
Meal | Dietary plan | Macronutrient composition |
Calorie intake |
---|---|---|---|
Breakfast | Meal replacement |
15% protein, 60% carbohydrate, 25% fat | 250 (200–300) kcal |
Morning snack | 3 dcl of smoothie (spinach, berries, or other seasonal local fruits) or 2-3 portions of seasonal fruits | 10% protein, 80% carbohydrates, 10% fat | 150 (100–200) kcal |
Lunch | Centered around starches; 4-5 food groups (whole grains: brown rice, pasta, buckwheat, millet, and corn; legumes: lentil, bean, and pea; tubers and pumpkins: potato and sweet potato; brassica: broccoli, cauliflower, kale, and cabbage; color and leafy vegetables: tomato, green salad) | 15% protein, 80% carbohydrate, 5% fat | 500 (450–550) kcal |
Afternoon snack | Sandwich (whole-grain bread, humus, tomato, kale, or cabbage) or millet with mixed berries or seasonal local fruits (if not already for morning snack) | 8–20% protein, 68–88% carbohydrate, 8–12% fat | 250 (200–300) kcal |
Dinner | Mixed green salad: green leafy vegetables, boiled potato, tomato, walnuts, or what was left from lunch and always meal replacement | 17% protein, 60% carbohydrate, 23% fat | 300 (200–400) kcal |
All participants were followed at weekly intervals. Evaluation of dietary diaries describing meal composition and food intake self-reports in the form of meal photographs were used to monitor compliance and correct and adjust deviations from the dietary plan and to help participants prepare the meals according to the dietary plan. Weekly lectures about the rationale and guidance on attaining the low-fat plant-based diet were given to all subjects (intervention and control group). Participants were encouraged to engage in at least two weekly sessions of 45 minutes of moderate-intensity exercise activity. Guided 45-minute moderate-intensity exercise sessions were organized for those who opted in and written exercise program to mimic guided sessions at moderate intensity was given to participant not attending the guided sessions. During the 10-week program 80% of all participants (intervention and control group) attended these exercise sessions.
Results are presented as means ± SD for normally distributed and as medians (range) for nonnormally distributed variables. Differences between groups were tested with
325 subjects were included in the analysis, 282 (87%) females and 43 (13%) males with average age of
Demographic characteristics of control and interventional groups.
Parameter | Whole sample | Control group | Intervention group |
|
---|---|---|---|---|
( |
( |
( |
||
Age (years) | 40 (18–71) | 41 (18–71) | 40 (19–69) | 0.98 |
Sex (female/male (%)) | 282/43 (87%/13%) | 74/10 (88%/12%) | 208/33 (86%/14%) | 0.68 |
Height (cm) | 167 (152–200) | 168 (153–200) | 167 (152–193) | 0.9 |
Weight (kg) | 77.7 (48.8–149.1) | 73.7 (49.2–139.3) | 79.3 (48.8–149.1) | 0.02 |
Smoking ( |
19 (6%) | 4 (5%) | 15 (6%) | 0.79 |
Married or living with a partner ( |
250 (77%) | 57 (68%) | 193 (80%) | 0.02 |
University educational level ( |
117 (36%) | 21 (25%) | 96 (40%) | 0.02 |
Frequent exercisers |
26 (8%) | 3 (4%) | 23 (10%) | 0.08 |
For normally distributed variables the data are given as mean ± SD and for nonnormally distributed variables as median (range).
Baseline body composition indices.
Parameter | Females | Males | ||
---|---|---|---|---|
Control group | Intervention group | Control group | Intervention group | |
( |
( |
( |
( |
|
Weight (kg) | 72.8 (49.2–118.1) | 76.6 (48.8–149.1) |
83.7 (63.6–139.3) | 91 (65.5–140) |
BMI |
26.4 (17.7–42.6) | 27.5 (18.6–47.7) | 23.2 (20.1–34.8) | 28.9 (21.1–46.2) |
Body fat (%) | 34.3 (16.1–46.7) | 37.1 (18.1–53.8) |
15.5 (6.3–28.3) | 24.4 (11.3–37.4) |
Visceral fat (arbitrary units) | 5.5 (1–13) | 7 (1–16) |
4.5 (1–16) | 9 (1–24) |
Total body water (l) | 48.5 (39.9–61.3) | 46.9 (34.6–60.3) |
60.1 (49.6–66.8) | 53.4 (46.4–64.7) |
Muscle mass (kg) | 45.5 (35.5–65.1) | 46.2 (34.4-79.4) | 71.2 (52–95.9) | 65.8 (55.2–83.4) |
Muscle mass percent (%) |
62 (51–79) | 60 (44–78) |
80 (68–89) | 72 (60–84) |
Estimated basal metabolic rate (kCal) | 2310 (1750–3270) | 2330 (1770–4510) | 3390 (1910–4930) | 3250 (2790–4270) |
Since most variables were non-normally distributed the data are presented as median (range).
Participant flow through study phases.
Differences in body composition between final (study end) and baseline values are given in Table
The differences in body composition indices between final and baseline study values.
Parameter | Control group | Interventional group |
|
---|---|---|---|
( |
( |
||
|
|||
Weight change (kg) | −1.2 (−1.6 to −0.8) | −5.6 (−6 to −5.2) | <0.001 |
Body fat% change (difference in absolute % points) | −0.4 (−0.7 to −0.2) | −4.3 (−4.6 to −4.1) | <0.001 |
Relative body fat change (%) | −0.9 (−2.2 to 0.3) | −13.4 (−14.3 to −12.5) | <0.001 |
Visceral fat change (arbitrary units) | −0.1 (−0.2 to 0.01) | −1.6 (−1.7 to −1.5) | <0.001 |
Muscle mass change (kg) | −0.4 (−0.7 to −0.1) | −0.3 (−0.5 to −0.06) | 0.25 |
Muscle mass% change (% points) |
0.4 (0.1 to 0.7) | 4.2 (3.9 to 4.4) | <0.001 |
Total body water change (l) | 0.3 (0.1 to 0.5) | 3.1 (2.9 to 3.3) | <0.001 |
|
|||
|
|||
Weight change (kg) | −1.9 (−2.7 to −1.1) | −7.3 (−8 to −6.6) | <0.001 |
Body fat% change (difference in absolute % points) | −0.5 (−1 to −0.05) | −3.8 (−4.2 to −3.4) | <0.001 |
Relative body fat change (%) | −1.1 (−2.2 to 0.03) | −9.6 (−10.8 to −8.5) | <0.001 |
Visceral fat change (arbitrary units) | −0.4 (−0.6 to −0.2) | −2 (−2.2 to −1.8) | <0.001 |
Muscle mass change (kg) | −0.7 (−1.4 to 0.05) | −0.9 (−1.3 to −0.5) | 0.85 |
Muscle mass% change (% points) |
0.004 (−0.002 to 0.01) | 0.04 (0.03 to 0.04) | <0.001 |
Total body water change (l) | 0.2 (−0.2 to 0.6) | 2.8 (2.5 to 3.1) | <0.001 |
Mean differences with 95% confidence intervals are shown. In the BMI 30 or more there were 30 subjects in the control group and 89 subjects in interventional group.
Analysis of covariance with adjustment for baseline values, age, and sex.
Parameter | Adjusted difference between interventional and control groups | 95% confidence interval |
|
---|---|---|---|
Final weight (kg) | −4.5 | −2.8 to −6.2 | <0.001 |
Final body fat% (% points) | −4.9 | −3.7 to −6.1 | <0.001 |
Final visceral fat (arbitrary units) | −2 | −1.5 to −2.5 | <0.001 |
Final muscle mass (kg) | 0.5 | −0.6 to 1.5 | 0.37 |
Final muscle mass percent (% points) | 4.6 | 3.4 to 5.8 | <0.001 |
Final total body water (l) | 3.6 | 2.6 to 4.6 | <0.001 |
For every dependent final variable in the first column the difference between interventional and control group was adjusted for baseline value of that variable, age and sex (analysis of covariance with general linear model ANOVA). Results and statistical significance remained materially unchanged when analyses were repeated separately for both genders.
The intervention group lost a significantly larger amount of weight, body fat, and visceral fat. In addition, the relative proportion of muscle mass and total body water increased relative to the control group. Even though the intervention group lost a significant amount of body weight and fat, muscle mass loss was negligible and this contributed to an increase of the relative proportion of muscle mass.
In the period of 10th–20th May 2016, at the median time lag of 17.4 months (range 3.4–64.2) after the end of the program, subjects were surveyed to obtain data on current body weight. Seventy-two participants (22%) did not respond, 78 participants (24%) responded but did not want to reveal their current weight, and 175 participants (54%) responded (31 participants from the control group and 144 participants from the intervention group). Mean body weight change from the end-of-program to time of follow-up survey was
Weight change of cases and controls at the late follow-up. First tertile of follow-up was 0–13 months after the end of the program and second tertile 13–25 months.
In the present study we report the effects of a dietary intervention combining two potentially efficient approaches for optimization of human diets: a low-fat, plant-based diet and plant-based meal replacements. Our key findings include a significant reduction in fat mass, visceral fat, and body weight and, importantly, a negligible decrement in absolute muscle mass with an increment in muscle mass proportion. Improvements were statistically significantly different in the intervention group compared to the control group; however, even in the control group some significant beneficial effects such as minor reductions in body weight and fat mass were observed.
Studies with vegetarian diet interventions were shown to result in a mean change in body weight of −3.4 kg (95% CI −4.4 to −2.4 kg) [
In this study we documented that muscle mass was well preserved, despite a significant and relatively large weight reduction and a relatively moderate protein content (approximately 15% of total daily calories from protein). Muscle mass loss in the intervention group constituted only 3.6% of total weight loss and 12.3% of weight loss in the subsample of obese subjects. Preservation of muscle mass in weight reduction programs is important due to the association of lean and muscle mass with resting metabolism level [
Meal replacement usage in weight management programs is associated with simplification of diet preparation and may improve the long-term success of a diet plan [
Our study has some obvious limitations inherent to studies of free-living subjects. The adherence to a diet plan could only be assessed from the subjective diaries and food intake self-reports, which are prone to underreporting of energy intake, especially in obese people [
Our study documents the body composition effects of the combination of two dietary approaches for human weight loss—an ad libitum consumed low-fat plant-based diet, which is supplemented with meal replacements. Prescription of this dietary intervention to free-living subjects for a duration of 10 weeks and without prespecified calorie counts and calorie restrictions resulted in significant reductions in body fat, visceral fat, and total body weight. The magnitude of weight reduction was above the average weight reduction reported for vegetarian diet interventions [
Barbara Jakše and Stanislav Pinter are receiving royalty compensation at Herbalife Int. Other authors declare no conflicts of interests.