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The “Skinny” on Milking Your Diet
By: Tara Kane
October 10th, 2008
Throughout history, milk has been an important part of the American diet. Glasses accompanied most family dinner tables and often complemented grandma’s homemade chocolate-chip cookies. Recent studies suggest, however, that the value of milk as a staple in the family diet has declined. In 2004, Nielson and Popkin conducted an analysis of American beverage consumption between 1977 and 1996. They found that for all Americans, the mean servings of milk decreased from 2.95 servings in 1977 to 2.21 servings in 1996, while the mean servings of sweetened beverages increased from 1.96 servings to 2.39 over the same time span. Even last year, in 2007, the NPD Group revealed that only about 40% of American children drank milk at dinner while nearly 30% had a soft drink or fruit juice with their meals (http://www.whatsnewiningredients.com/Food-Ingredients/Articles.aspx/16434).
One consequence of these recent trends in beverage consumption is that more Americans today are overweight and obese than ever before. According to the National Center for Disease Control, the prevalence of obesity rises every year. Currently, over one third of today’s adult population and nearly one fifth of children and adolescents fall under the weight category of obese. Being overweight and obese has serious effects on the health of Americans such as raising the risk for certain diseases like heart disease and diabetes and increasing the chances of having high blood pressure (http://www.cdc.gov/nccdphp/dnpa/obesity/index.htm). Due to these many health risks associated with obesity, social concern over nutrition and lifestyle has become very widespread.
A more adults and children choose soft drinks and juice over milk a higher number of people are, in essence, consuming “empty calories.” Though similar in caloric number to milk, soft drinks and fruit juices are typically loaded with sugar and devoid of vitamins and minerals. Milk, on the other hand, is sweetened naturally and contains nine essential nutrients for the body (http://www.whymilk.com/health_facts_nine.php). Of the nine, calcium, vitamins A and D, and protein occur most abundant. Calcium strengthens bones and teeth, vitamin D aids in bone building, vitamin A keeps skin healthy, and protein builds and maintains muscle tissue. Because of these nutrients, drinking the recommended amount of milk has many proven health benefits such as a decreased risk of osteoporosis later in life and fewer bone fractures (http://www.whymilk.com/health_staying_bone.php).
In an effort to promote more milk drinking nationwide, America’s Milk Processors with The Campaign for Healthy Weight have asked Americans if they “Got Milk?” For many years “Got Milk?” advertisements have appeared gracing the pages of popular women’s magazines such as SHAPE and Woman’s Day, as commercials on national television, and more recently on websites such as www.WhyMilk.com. Today both the slogan “Got Milk?” and the “milk mustache” are famous in popular culture thanks to all of the well-known celebrities, public figures, musicians, and professional athletes who have been featured in the campaign. Every ad features a celebrity photographed wearing a milk mustache and a quoted statement in support of drinking milk for your health. In this way, the public eye receives a positive image of milk drinking through the people who are not only role models for achievements, but for their health, thinness, beauty, and athleticism as well.
Most recently, Suze Orman, Serena Williams, Trisha Yearwood, Glenn Close, and Ali Vincent have worn a milk mustache. Serena Williams, as a professional athlete and a woman, receives world-renowned recognition for her exceptional ability on the tennis court and high regard for her physical discipline off the court. In her advertisement , Serena appears with a milk mustache looking as she would on the tennis court except that she is holding a glass of milk. Under the title, “Lean Machine,” the ad reads (http://www.whymilk.com/pdf/ad_williams.pdf):
“When it comes to winning titles, perfect form helps. So I serve up milk. Studies suggest people pursuing a healthy weight could lose more weight and burn more fat by including 24 ounces a day of low-fat or fat free milk in their reduced-calorie diet, instead of 8 ounces or less. That’s what I call a nice return.”
Within her statement Serena makes two claims to the public consumer: 1) she attributes her success on the court to milk drinking and 2) she suggests a positive association between drinking milk and losing weight. But, in a society that consumes milk less than ever before and where the prevalence of obesity continues to grow, is the suggestion that people could lose more weight and burn more fat by including 3 servings of low-fat or fat free milk in their reduced-calorie diet really a legitimate health claim? Or, is it merely a faux paux scheme to convince people to drink more milk and increase profits for the dairy industry?
Evidence in Support: “Weighing in on the American Diet”
To provide evidence for their “Got Milk?” claim, The Campaign for Healthy Weight cites the key findings from a recent report called Weighing in on the American Diet and several other studies analyzing children, teens, and adults on their website. Weighing in on the American Diet compiled data from consumer research collected in November of 2007 and from five NPD Group databases such as National Eating Trends to create a comprehensive snapshot of American dieting and the weight management practices used (http://www.whymilk.com/pdf/ExecutiveSummary.pdf). One of the report’s many key findings is that dieters who drank low-fat or fat free milk as a daily habit were more likely to be at a healthy weight (a BMI between 18.5 to 25) and have diets richer in essential nutrients compared to those who didn’t (http://www.whymilk.com/report_findings.php). Though significant, these results are rather broad because they apply to the general population of Americans, most of whom are adults.
To include more population-specific evidence, the campaign accompanies the general findings of Weighing in on the American Diet with a separate section highlighting individual research efforts on children, teens, and adults. Among the three articles cited under the “children” heading, two, “Not Getting Enough Milk and Dairy during Preschool Years May Lead to Weight Gain in Adolescence” and “Low Calcium Intake Linked to Higher Body Fat in Children”, suggest a negative correlation between dairy consumption and a child’s weight (Moore, 2006, and http://www.whymilk.com/health_weight_children_02.php). Both studies look at how milk affects the chances of a child becoming overweight and its affect on body fat levels. Neither, however, seems to address weight loss directly, only the potential for weight gain by not drinking enough milk.
Similarly under the heading “teens,” only two articles seem relevant to the milk and weight loss claim by hinting that daily milk drinkers are generally slimmer than those who consume less milk. The article from the Journal of Nutrition, “Teen Milk Drinkers are Slimmer,” found that among girls aged 9-14, those who consumed more milk and dairy had slimmer figures than their counterparts (http://www.whymilk.com/health_weight_teens_03.php). In the other article, “New Research Shows Beverage Choice Significantly Impacts Weight and Nutrient Intakes of Adolescent Girls,” lower BMI was correlated with higher milk intake (Striegel, 2006). Evidence is only cited on adolescent girls, so it remains unclear whether milk drinking affects weight and BMI in teen boys the same way.
Unlike the evidence cited for children and teens, many of the adult studies directly pertain to the link between milk and weight loss. One, “New Research Supports Milk’s Role in Weight Loss,” discovered that, among people on reduced-calorie diets, those who drank 3-4 servings of milk lost significantly more weight than people who drank little or no milk (http://www.whymilk.com/health_weight_adults_09.php). Similarly, “New Study Strengthens Milk’s Fat Burning Link,” compared the metabolisms of adults on a reduced-calorie diet who consumed 3-4 servings of dairy and exercised with another group who exercised and only consumed 1-2 servings (Melanson et al., 2005). The experiment revealed that the adults who consumed 3 to 4 servings of dairy foods daily subsequently burned more fat than the group who consumed less. Among adults, at least according to www.whymilk.com, it seems that a body of legitimate scientific research exists to support the “Got Milk?” claim that consuming 3 servings of low-fat or fat free milk a day can improve weight loss.
Looking Beyond WhyMilk.com
A decent body of scientific literature examining milk and dairy’s affects on weight exists outside of the website. Some, like those cited on the website, support the link between milk and weight loss. A cross-sectional study of over 400 healthy, randomly-selected Tehranian adults by concluded that an inverse relationship exists between milk consumption and body mass (Mirmiran, Esmaillzadeh, and Azizi, 2005). In assessing the relationship, the researchers collected dietary data from the adults, recorded their heights, weights, and BMI’s, and measured their physical activity by the Lipid Research Clinic questionnaire. They found that after controlling for the effect of age, physical activity, energy, carbohydrate, dietary fiber, protein, and fat intake, the proportion of obese subjects declined as dairy intake increased, while the proportion of normal-weight subjects rose. Moreover, those who consumed more servings of dairy recorded lower BMI’s than those who consumed less. Though the study examined Tehranian adults, the researchers considered and controlled for many potential confounds. Thus, the study has important implications regarding the possible effects of increased milk consumption on weight loss in American adults.
The evidence provided by Mirmiran, Esmaillzadeh, and Azizi (2005) seems positive, but a large proportion of the available research on milk and weight loss suggest otherwise. In their longitudinal study of over 12,000 children aged 9-14, Berkley et al. (2005) analyzed the associations between milk, calcium, dairy fat, and weight change. From 1996-1999, the children annually reported their height and weight measurements to the researchers and returned a questionnaire about food frequency. Then after adjusting for adolescent growth and development, race, physical activity, inactivity, and total energy intake, associations between annual change in body mass index and the dietary factors were estimated. Contrary to the “Got Milk?” claim, the researchers discovered that, over time, children who drank more milk (more than 3 servings of 1% or skim milk a day) gained more weight than those who only drank 1-2 servings.
Moreover, aside from many primary research reports like Berkley et al.’s (2005), a number of review papers exist assessing the possible effects of dairy intake on the body weight or composition of both children and adults. At least one review by Lanou and Barnard (2008) and another by Barr (2003) concluded that the current data available from clinical trials provides little support for the hypothesized association between calcium or dairy consumption and weight loss. In their study, Lanou and Barnard (2008) argued that cross-sectional designs assessing dairy and weight do not provide adequate evidence for weight loss because they only capture data from one point in time, but find that more appropriate longitudinal studies often result inconclusively. So to further assess the connection between dairy and weight loss, the researchers conducted a MEDLINE search for clinical trials which addressed calcium or dairy supplementation in adults or children in both dieting and non-dieting conditions. Of the 49 randomized trials examining dairy or calcium supplementation that they located, 41 revealed no significant effect between dairy and body weight with or without dieting. One study suggested a greater rate of weight loss with supplementation, while two demonstrated weight gain. Only four trials actually resulted in weight loss, but the weight loss was differential and participants were under calorie-restriction.
In a similar piece conducted by Barr (2003), just one out of the 26 total studies reviewed showed a positive effect of dairy and calcium supplementation on weight loss. Between 1966 and 2001, Barr (2003) searched MEDLINE for articles exploring calcium or dairy products and body weight or body composition. The search resulted in a total of 17 studies on calcium supplementation and 9 on dairy product supplementation. Out of the 17 calcium studies, only one found evidence for weight loss, most likely by chance. In the 9 that supplemented dairy, the body weights and compositions of the treatment and control groups remained relatively the same. While it was, however, not often taken into account that energy intake from food differs by the individual, overall, the review provided little evidence to support the hypothesis suggesting that calcium or other components of dairy products can lead to weight loss.
So What Does This All Mean?
Clearly, milk “does the body good”: it’s packed with calcium, loaded with protein, and a good source of vitamins A, D, B12. In the recommended amounts, these essential nutrients help build strong bones while keeping your body looking and feeling healthy. Studies have linked higher milk intake with reductions in bone fractures, lower risk for cancer in women, and lesser likelihood of developing diabetes. Moreover, it has been suggested by “Got Milk?” ads that people who drink 3 servings of protein-rich, low-fat or fat free milk a day build lean, fat-burning muscle tissue and lose more weight than people who consume less. Throughout, this paper has sought to address whether milk could really be the key to a new revolution in weight loss.
Of the outside literature assessing this claim, most report that consuming 3 servings of milk or more positively affects the health of subjects, except, as far as weight loss is concerned. Like the situations with many health claims, the scientific evidence surrounding milk and its connection to weight loss is contradictory. Some individual clinical trials did indeed find that subjects who consumed more milk lost more weight than their counterparts who drank less. In these trials, however, participants were often overweight or obese and analyzed while restricted under a reduced-calorie diet. Other literature, such as review papers over many clinical trials, concluded that there is little evidence to support the milk and weight loss hypothesis. Most cited no significant difference in weights or BMI’s between the treatment groups and the control groups. Thus, it would probably be more justified to argue that 3 servings of low-fat or fat free milk a day can help people maintain weight, rather than lose it.
Ironically last year, in fact, the National Dairy Council agreed to drop the ads in their $200 million-plus campaign promoting milk’s aid to weight loss following scrutiny from the Physicians Committee for Responsible Medicine (Anonymous, 2007). PCRM, which promotes dieting free of animal products, sent a petition to the Federal Trade Commission claiming that there was not enough conclusive evidence to support a weight-loss claim for dairy products. In the end, the FTC ordered the Dairy Council to change the ads until further research is done on the association between drinking milk and weight loss. Further research should assess the impact of higher milk intake combined with physical exercise on body composition before reasonable conclusions can be made in support of the claim.
Anonymous. (2007). Dairy Group Sheds Weight-Loss Ads. Tufts University Health & Nutrition
Letter, 25(5), 3.
Barr, Susan L. (2003). Increased Dairy Product or Calcium Intake: Is Body Weight or
Composition Affected in Humans? Journal of Nutrition, 133(1), 245S-248S.
Berkey, Catherine S. et al. (2005). Milk, Dairy Fat, Dietary Calcium, and Weight Gain: A
Longitudinal Study of Adolescents. Arch Pediatr Adolesc Med., 159(6), 543-550.
Lanou, Amy Joy and Neil D. Barnard. (2008). Dairy and Weight Loss Hypothesis: An
Evaluation of the Clinical Trials. Nutrition Reviews, 66(5), 272-279.
Melanson, EL, et al. (2005) Effects of Low- and High-calcium Dairy-based Diets on
Macronutrient Oxidation in Humans. Obesity Research, 13, 1-11.
Mirmiran, P., A. Esmaillzadeh, and F. Azizi. (2005). Dairy Consumption and Body Mass Index:
An Inverse Relationship. International Journal of Obesity, 29, 115-121.
Moore LL, et al. (2006) Low Dairy Intake in Early Childhood Predicts Excess Body Fat Gain.
Obesity, 14, 1010-1018.
Nielson, Samara Jay, and Barry M. Popkin. (2004). Changes in Beverage Intake Between 1977
and 2001. American Journal of Preventative Medicine, 27(3), 205-210.
Striegel, RH et al. (2006). Correlates of Beverage Intake in Adolescent Girls: the National Heart,
Lung, and Blood Institute Growth and Health Study. Journal of Pediatrics, 148, 183-187.
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