“Reversing childhood obesity ought to be a national priority.” (1) This statement, made last June by Marion Nestle, a noted public health nutritionist, would be hard to disagree with considering that more than one third of American children are either overweight or obese. (2) But what may be hard to agree upon is the best way to accomplish this goal.
While the increasing rate of childhood obesity seems to have leveled off, there is a growing consensus that much more needs to be done, and at earlier ages if we hope to have an impact. In my last blog, I wrote about a newer approach to preventing childhood obesity: providing nutrition education to preschool-aged children. One major concern I have with this approach is that we do our best to get the education right, as teaching children the wrong information will most certainly be worse than doing nothing at all.
Good Intentions, Insufficient Science
The authors of the 2011 Institute of Medicine report “Early Childhood Obesity Prevention Policies” do not appear to share my concern. Faced with a paucity of experimental studies, the IOM committee has, in their words, given consideration to strong observational studies and acknowledged they were receptive to evidence that a policy would be likely to affect a determinant of childhood obesity even if not studied for its direct influence on obesity in children. In an apparent effort to take some action, they decided that “despite the scarcity of data, the urgency of the issue of obesity in young children demands that action be taken now with the best available evidence.” (3) Scarcity of data and reliance on studies that only can show correlation, not causation—is this a sound basis for a population-wide, early childhood nutrition initiative?
The IOM committee summed up their opinion as follows: “obesity prevention actions should be based on the best available evidence—as opposed to waiting for the best possible evidence.” (3) That sounds oddly familiar to the decision made by the Senate Select Committee on Nutrition, which convened in the late 1970s. Although at the time the evidence implicating saturated fat and cholesterol in cardiovascular disease was being debated, the government committee decided to proceed in recommending low-fat, low-cholesterol diets for the entire population. According to committee chair George McGovern, “We Senators don’t have the luxury that a research scientist does of waiting until every last shred of evidence is in." (4) That hasty decision may actually be one of the major contributors to the increased prevalence of overweight and obesity we have observed over the past three decades, including among children.
The IOM committee also concurred with the conclusion of a 2010 study of children ages 2-18, by stating that “even the nation’s youngest children are consuming diets that are too high in energy and added sugar, fat, and salt and that include too few fruits, vegetable, and complex carbohydrates.” The authors of the 2010 study include whole milk, regular cheese, and fatty meats in their sources of empty calories from added fat, in accordance with the recommendations of the 2005 Dietary Guidelines for Americans. (5) They also indicate that “whole milk has more nutrient-dense alternatives: fat-free milk/and or reduced fat milk.” Fortunately, the Dietary Guidelines are not intended for children under 2, and the American Academy of Pediatrics still recommends whole milk up until 2, with low-fat after that. (Even so, I have seen more than a few toddlers inappropriately put on fat-free dairy and lean meat by their referring pediatrician in an effort to curb their weight gain.)
Will discouraging whole milk consumption help?
One significant concern about the IOM approach is that whole milk consumption actually seems to have a wide range of beneficial effects, including an inverse association with overweight/obesity in children and adults. Whole milk also contains important fat-soluble nutrients which may be inadequate in many children’s diets. (6) (7)
Recently, Ludwig and Willet questioned the widely accepted “evidence-based” recommendation for reduced-fat milk for children, citing studies that found:
- A primary focus on reducing [overall] fat intake does not facilitate weight loss;
- Consumption of low-fat, high glycemic diet may adversely affect [caloric] expenditure;
- Prospective studies in young children observe greater rates of weight gain with the consumption of reduced-fat compared with whole milk. (8)
While Ludwig and Willett are not proponents of animal milk for human consumption, other researchers have shown that populations that consume full fat dairy have a survival advantage (9), probably in part because it is a good source of protein and other essential nutrients (8) including numerous bioactive proteins, fats, and other components that positively impact health. (10) It is also recognized that several of these components, while not recognized as essential nutrients, actually enhance utilization of the minerals and vitamins present. (10) Our understanding about the real benefits of full fat dairy may still be in its infancy.
The most recent study on milk type and weight status in 2-4 year olds showed a negative association between dairy fat and body fat; in other words, drinking 1% or skim milk was more common among overweight preschoolers, and did not in fact slow weight gain for overweight children between the ages of 2 and 4. The authors noted that it is not possible to determine if parents give their already overweight preschoolers low-fat and skim milk to help improve their weight, or if the consumption of low-fat milk contributes to weight gain. In any case, it does not appear that low-fat milk helps preschoolers maintain a normal body mass. The authors speculated that dietary fat, through its effect on satiety hormones, may lead to lower caloric intake. (11) Unfortunately, there are no published randomized trials testing the effect of dairy fat on the weight of preschoolers.
Although such studies may never be done due to ethical constraints, the relevant studies reviewed here indicate that whole milk has a beneficial or at least neutral effect on weight in children. And since the IOM committee seems to have got it wrong about dairy fat, can we be confident in their other recommendations to prevent childhood obesity? The reasons behind this epidemic are clearly more complex than the simple “calories in, calories out” equation can explain.
You might be thinking, so what if whole milk does not contribute to weight gain, doesn’t dairy fat promote cardiovascular disease? And really, how important are the nutrients in dairy fat for growth and development? I will discuss these issues in upcoming blog posts, as well as the possible negative impacts that any dietary intervention that labels foods as either “healthy” or “unhealthy” could have on young children in regard to eating habits and body image.
1. Ogden CL, Carroll MD, Kit BK, Flegal KM. J Am Med Assoc. 2012;307(5):483-490.
2. Nestle M. JAMA Pediatr.2013; 167(6):584-585.
3. Institute of Medicine (IOM). 2011. Early Childhood Obesity Prevention Policies. Washington, DC: The National Academies Press. Note: The IOM is a non-governmental non-profit organization founded in 1970, under the congressional charter of the National Academy of Sciences. It provides national advice on issues relating to biomedical science, medicine, and health, serves as adviser to the nation to improve public health.
4. An excellent overview, although not a primary source: http://www.abovetopsecret.com/forum/thread654969/pg1. Tom Naughton’s Fathead Movie has a nice explanation of this including actual news footage: http://www.youtube.com/watch?v=xbFQc2kxm9c.
5. Reedy and Krebs-Smith. J Am Diet Assoc. 2010; 110(10): 1477–1484.
6. Kumar J, Muntner P, Kaskel FJ, Hailpern SM, Melamed ML.
7. Gutierrez Y, Jackson PL, Stephens D. Subclinical vitamin A deficiency: a potentially
unrecognized problem in the United States. Pediatr Nurs.1996;22(5):377-389.
8. Ludwig DS, Willett WC. JAMA Ped. 2013;167(9):788-789.
9. Elwood PC, Givens DI, Beswick AD, Fehily AM, Pickering JE, Gallacher J. J Am Coll Nutr. 2008;27(6):723S-34S.
10. Ward RE, German JB. J. Nutr. 2004;34:962S–967S.
11. Scharf RJ, Demmer RT, DeBoer MD. Arch Dis Child.2013;98:335-340.