Mattes suggested that the message in the media to “load up” on fruits and vegetables as a way to lower weight is misleading without considering overall energy intake. The Nurses Health Study, for example, which tracked almost 75,000 people over a 12-year period, showed that greater fruit and vegetable intake led to lower weight gain in women but not reduced weight for participants or for their children (He et al., 2004). Greater fruit and vegetable consumption alone will not reduce weight without the qualification to moderate energy intake.
The next food category that Mattes discussed was whole versus refined grains. The line of reasoning behind encouraging consumption of whole grains is that they are higher in fiber and increase satiety, and therefore, people will eat less. Data from the Nurses Health Study indicate that greater intake of whole grain products was associated with reduced weight gain but provided little or no benefit for weight loss compared to consumption of refined grain products over the course of the 12-year study period (Liu et al., 2003). Other recent studies, both short and longer term, have shown similar results.
Drinking reduced-fat versus whole milk does not benefit weight management. Higher-income people purchase more low-fat milk and lower-income people purchase more whole milk, even when prices are the same, according to the Continuing Survey of Food Intake by Individuals (CSFII). The prevailing belief is that weight improves by switching to lower-fat dairy products. However, the Growing Up Today study (Berkey et al., 2005) and the National Health and Nutrition Examination Survey (Beydoun et al., 2008) actually show an increase in body mass index among children who drink fat-free and low-fat milk. This may reflect reverse causality in that heavier individuals choose lower-fat products to manage their weight, but it cannot be concluded that simply including lower-fat dairy products in the diet or substituting them for higher-fat products will promote weight loss.