|Do Meal Replacements Deliver Results?
'Research finds that some meal replacement products are effective for temporary weight loss'
Michelle Kulovitz, M.S. and Len Kravitz, Ph.D.
Exercise professionals frequently inspire each of their clients to adopt a lifestyle filled with regular physical activity, positive behaviors and a healthy eating plan. With clients who have weight loss goals, three potential options for an energy-reduced dietary plan are often discussed. A reduced calorie diet (RCD) is a low calorie approach (1200-1600 kilocalories per day) that often involves having a dietician or clinical nutritionist prescribe a food regimen to follow (Heymsfield et al., 2003). Heymsfield and colleagues indicate that a second option is a meal plan of prepackaged foods and snacks that are vitamin/mineral fortified. The third option is a partial meal replacement, where one or more portion-controlled (vitamin/mineral fortified) meals are incorporated with at least one daily meal of regular foods. This column will explore the scientific literature on meal replacements in determining their efficacy for personal trainers to use with clients.
What are Meal Replacements?
Meal replacements (see Side Bar 1 for more) may include beverages, prepackages of shelf-stable and/or frozen entrees, breakfast cereals, and meal/snack bars that are eaten to replace a higher calorie meal (Heymsfield et al., 2003). Heymsfield and colleagues assert that they may be used as the sole energy source or with a combination of foods. Commercial meal replacements are often marketed as vitamin, mineral, and protein fortified foods. They are sometimes combined in a RCD to reach the desired daily caloric deficit (Heymsfield et al., 2003). Products such as Slimfast ©, Special K ©, Lean Cuisine ©, and many others are meal replacements often marketed to people who are interested in losing weight.
Is a Single Meal Replacement an Option to Consider?
A recent randomly controlled research study by Levitsky and Pacanowski (2011) suggests that the mere substitution of one smaller portioned meal each day is sufficient to elicit a meaningful reduction in daily energy intake. Subjects recruited by Levitsky and Pacanowski chose to eat one of the following for lunch for 10 days: Chef Boyardee © pasta, Smucker's Uncrustables ©, or a Kashi © bar while maintaining normal intake for all other meals. This resulted in an average reduction in energy intake of 250 calories per day (2057 ± 47 kilocalories to 1812 ± kilocalories).
Waller et al. (2004) investigated the effect of a ready-to-eat breakfast cereal as a nightly structured snack replacement. The research team randomized 25 adults (18-65 yrs, BMI &Mac179; 25) into a cereal and no-cereal group. All subjects reported having evening snacking behaviors. The cereal group had a ready-to-eat cereal with low-fat skim milk 90 minutes after their evening meal and the no-cereal group snacked on foods of their choice. After 4 weeks the cereal group lost 1.85 lbs vs .39 lbs for the no-cereal group. Many exercise professionals have overweight and obese clients with night snacking behaviors (as Waller et al report this is common with this population) and may choose to discuss similar options with these clients.
Heymsfield et al. 2003 emphasize that many strategies for weight reduction demonstrate promising short-term results, yet longer term (&Mac179; 1 year) research still shows a high degree of weight relapse, where clients regain the weight. In a past IFJ column (Kravitz, L. (2009). IDEA Fitness Journal, 6(10), 18-20), research was highlighted that shows consistent physical activity is the best predictor of sustained weight management after weight loss. Consequently, personal trainers are crucial to helping clients achieve long-term success in weight management.
What is the Scientific Assessment of Meal Replacement Strategies for Weight Loss?
The use of these pre-measured lower calorie products to facilitate a RCD has been shown to be most effective for weight loss (Levitsky and Pacanowski, 2011). In a meta-analysis done by Heymsfield et al. (2003) on meal replacements, the researchers examined six studies that met strict research methodology criteria. The authors concluded that partial meal replacement programs can be safely and effectively utilized, and are shown to improve weight-related risk factors of disease in addition to subjects losing about 7-8% of initial weight over the course of a year.
Will you be Hungrier on Meal Replacements?
It has been submitted that individuals who consume fewer calories during one meal replacement may compensate for the calorie deficit at the subsequent meal (Levitsky and Pacanowski, 2011). This does not appear to be the case. Although a true mechanism is unknown at this time, Levitsky and Pacanowski propose that people may adapt to the meal replacement as the 'norm' for the meal. Thus individuals may make behavioral modifications that reduce the need to consume more food. Also, the visualization of a smaller portion controlled meal may help individuals slow down while eating and pay more attention to internal cues of satiety. Future studies are warranted to determine any physiological mechanisms associated with meal replacement plans and appetite.
Are Meal Replacements Safe for Individuals with type 2 Diabetes?
The Look AHEAD trial (Pi-Sunyer et al., 2007) is an ongoing study of 5,145 overweight subjects with type 2 diabetes undergoing a lifestyle intervention for weight loss that includes 175 minutes/week of moderate intensity physical activity along with meal replacements (liquid meal replacements and frozen food entrees) combined with conventional foods. One-year results show the subjects have lost an average of 8.6% of initial body weight. Cardiovascular fitness has improved by 21% during the 12 months. In addition, subjects have shown a significant improvement in some biomarkers associated with metabolic syndrome.
Applications for the Exercise Professional
Exercise professionals are very aware that successful weight loss programs are multi-factorial approaches that include regular exercise, behavior modification, healthy nutrition education, portion control, and S.M.A.R.T. goal setting for clients. Meal replacements are proving to be a successful option for creating dietary caloric deficits. However, for prolonged weight regain prevention the exercise professional's role is truly paramount in motivating clients to maintain their reduced body weight.
Side Bar 1: How to Choose an Effective Meal Replacement?
Meal replacement products can be found at the local grocery store and/or supplied by a medical or weight loss professional. Key points to check include:
1) Meal replacements should be between >100 to <230 kilocalories
2) Although debatable in the research, meal replacements with protein (12-20 grams per serving) may keep some people full for a longer period of time (3-4 hours)
3) Be aware of meal replacement bars and shakes with high sugar content
4) Look for fortified with a third of the daily vitamins and mineral
5) Some examples of products that can be found in a local grocery/health food store that meet these guidelines above are:
Kashi GoLean ® breakfast cereal (1 cup serving): Calories=190, Protein=13g, Fat=1g, Fiber=10g
Kashi GoLean ® Roll Bar, Oatmeal Walnut (1 bar serving): Calories=190 Protein=12g, Fat=5g, Fiber=6g
Luna Protein ® Cookie Dough (1 bar per serving): Calories=170, Protein=12g, Fat=6g, Fiber=3g Detour ® Caramel Peanut (1 bar serving): Calories=170, Protein=15g, Fat=5g, Fiber=2g
Pure Protein ® Chocolate Deluxe (1 bar serving): Calories=180, Protein=20g, Fat=4.5g, Fiber=2g
Lean Cuisine ®: Grilled Chicken Primavera Pasta (1 entrée serving): Calories=220, Protein=17g, Fat=4g, Fiber=5g
SlimFast ® High Protein Creamy Chocolate (1/3 cup scoop serving): Calories=200, Protein=15g, Fat=4g, Fiber=4g
Side Bar 2: Three Common Questions About Meal Replacements
1) Should anyone start a reduced calorie diet with meal replacements? No, before starting a reduced calorie diet it may be beneficial for the client to consult her/his doctor about the weight loss plan, especially if there is a pre-existing health condition. In addition, medications may need to be adjusted, especially for those persons interested in replacing two or more meals per day.
2) How long should a person use meal replacements? If utilizing one meal replacement per day a person can continue indefinitely, as long as he/she monitors intake at other meals to maintain a well-balanced diet. If the plan is to utilize two or more meal replacements per day it is recommended that the client seek the advise of a clinical weight loss specialist.
3) Are there options to consume ONLY meal replacements to gain greater and faster weight losses? Yes, these types of meal replacements are called full formula meal replacements and are the most aggressive when a person has a large amount of weight to lose. These are medical grade products that are formulated specifically to provide all recommended macro- and micronutrients during this RCD. These products are only available from a physician or weight loss center that specializes in medical weight loss.
Heymsfield, S.B., van Mierlo, C.A., van der Knaap, H.C., Heo, M., and Frier, H.I. (2003) Weight management using a meal replacement strategy: meta and pooling analysis from six studies. International Journal of Obesity, 27(5), 537-549.
Levitsky, D.A. and Pacanowski, C. (2011). Losing weight without dieting. Use of commercial foods as meal replacements for lunch produces an extended energy deficit. Appetite 57, 311-317.
Pi-Sunyer, X., Blackburn, G., Brancati, F.L., Bray, G.A. et al. (2007). Reduction in weight and cardiovascular disease risk factors in individuals with type 2 diabetes: one-year results of the look AHEAD trial. Diabetes Care, 30(6),1374-1383
Waller, S.M., Vander Wal, J.S., Klurfeld, D.M., McBurney, M.I., Cho, S., Bijlani, S., and Dhurandhar, N.V. (2004). Evening read-to-eat consumption contributes to weight management. Journal of American College of Nutrition, 23(4), 316-321.
Michelle G Kulovitz, MS is a doctoral candidate in Exercise Science at the University of New Mexico, Albuquerque. She currently holds a MS in Nutrition as well as a MS in Exercise Science. Her research
interests are in weight management and weight loss maintenance.
Len Kravitz, PhD, is the program coordinator of exercise science and a researcher at the University of New Mexico, where he won the Outstanding Teacher of the Year award. He has received the prestigious Can-Fit-Pro Lifetime Achievement Award and was chosen as the American Council on Exercise 2006 Fitness Educator of the Year.