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6 Key Factors that Predict Weight Gain
Troy Purdom, M.S and Len Kravitz, Ph.D.

Two-thirds of the U.S population is currently overweight or obese (Ogden et al. 2014), a health condition associated with several comorbidities, including hypertension, cardiovascular disease, diabetes, depression, and breast, endometrial, colon, and prostate cancers (Malik, Shulze and Hu, 2006). Further, research shows that Americans at the age of 50 tend to gain weight slowly over time, approximately one lb per yr (Mozaffarian et al. 2011). Most weight management articles focus on strategies and behaviors to lose weight. In this article, we examine the predictors of weight gain over the lifespan in hopes to better understand, prevent and manage obesity.

What Dietary Food Choices Influence Weight Gain?
Mozaffarian et al. (2011) identified that the regular dietary consumption of potato chips, potatoes (french fries, mashed, baked, and boiled potatoes), red meat, processed meats (bacon, salami, sausage and luncheon meats), unprocessed red meats (beef, hamburger, pork, lamb or game), butter, sweets and desserts to be associated with progressive weight gain over several different four-year period of times they studied. Gradual, yearly weight gain is also observed with the regular intake of refined grains, foods such as white flower and white rice. Intakes of foods such as nuts, whole grains, fruits, vegetables, yogurt, diet (zero-calorie) soda, cheese and milk (low-fat, skim and whole) appeared to curve weight gain. Mozaffarian et al. explain that these foods have slower digestion rates (some being high in fiber), and appear to enhance satiety (the feeling of being full after a meal). Their consumption can replace other, more highly processed foods in the diet, providing a reasonable biological mechanism whereby persons who eat more fruits, nuts, vegetables, and whole grains may gain less weight over time (Mozaffarian et al).

To What Effect Do Sweetened Beverages Influence Weight Gain?
Sugar-sweetened beverages (SSB), which have little nutritional benefit, are reported to provide the largest amount of kilocalories in the American diet (Dennis et al. 2009). In 2008 SSB accounted for 8-9% of total energy intake in both children and adults (Malik et al. 2008). SSB contain carbohydrates of various forms, such as high fructose corn syrup, sucrose and artificial sweeteners amongst others ingredients. The intake of SSB has little impact on satisfying hunger (Malik, Shulze and Hu, 2006). Thus, large amounts of calories in SSB can be ingested without suppressing appetite (Mattes 2006). Uniquely, the body responds to liquid carbohydrate vs. solid carbohydrate (of equal caloric value) differently. DiMeglio and Mattes 2000 found that when drinking SSB, people gained significantly more weight in comparison to consuming a comparable amount of carbohydrate in solid form. Subjects participated in both treatments for four weeks each, and the SSB treatment gained double the amount of fat mass compared to consuming carbohydrate in solid form. Both carbohydrate sources were the caloric equivalent to three 12-ounce sodas per day for both treatments (DiMeglio and Mattes).

What Influence Does Sleep Deprivation have on Weight Gain?
Although more clinical trials are needed, a number of epidemiological studies suggests that weight gain is influenced by sleeping less than 7 hours or more than 8 hours on a nightly basis (Marshall, Glozier, Grunstein 2008). According to Marshal et al. people who sleep less develop chronically impaired glucose metabolism, steadily contributing to obesity. In addition, sleep deprivation significantly LOWERS circulating hormone levels of leptin (promoting food intake) and INCREASES circulating hormone ghrelin (promoting food intake) (Van Cauter et al. 2008). The altered regulation of these hormones contributes to increased hunger and appetite, especially for carbohydrate-rich foods weight gain (Van Cauter et al.). Ideally, obtaining 7-8 hrs of sleep each night is a complement to a successful weight management program.

What Influence Does Watching Television Have on Weight Gain?
The length of time spent watching television is highly correlated with weight gain, especially in the youth (Chapman et al. 2012). Chapman et al. recap that 58.9% of Americans watch television for >2 hours/day. The authors summarize epidemiologic studies which reveal those who regularly watch more daily television tend to snack more while watching, have higher caloric intake of foods, and choose to consume more energy-dense foods, all leading to weight gain. Other evidence indicates that visual images of palatable food (as regularly seen in food commercials) evoke increases in plasma ghrelin concentrations, thus increasing the hunger/eating response (Chapman et al.). Conversely, children watching <1 hour of TV a day are associated with reduced body weights, BMIs, skin-fold thicknesses, and fat mass. And, these children are less likely to be overweight, emphasizing the important role of lifestyle plays with weight gain (Chapman et al.)

What is The Effect of Alcohol on Weight Gain?
Alcohol is very energy dense and therefore affects energy balance in a variety of ways. The energy density of alcohol is 7 kilocalories/g, second only to fat (9 kilocalories/g). Aside from the pharmacological effects on the brain and hormone fluctuation, the additional kilocalories from alcohol do not seem to replace energy consumption from other sources (Yeomans 2010). Therefore, energy consumption from alcohol is additive to the overall daily calorie intake. Yeomans adds that alcohol consumed before or with meals tends to also increase food intake, probably through enhancing the short-term rewarding effects of food. Uniquely, Yeomans cites epidemiological data suggesting that alcohol in moderation can protect against obesity, specifically in women. This means that alcohol is somewhat dose dependent, and should be monitored closely, especially while consuming food.

What is the Effect of inactivity on Weight Gain?
Exercise has long been shown to have positive effects on both health and weight loss. In studying 15-year trends, an inverse relationship was found between walking and weight gain (Gorden-Larsen et al. 2009); suggesting that the more a person walks the less likely she/he is to gain weight. The researchers point out that older Amish persons who walk an average of 18,000 (men) and 14,000 (women) steps a day have very little prevalence of obesity. Gorden-Larsen et al.. suggest that adding 2-4 hours of walking per week are attainable targets to achieve for movement.

Despite the documented benefits of exercise, only half of Americans participate in the recommended volume of (150min/wk) of moderate aerobic activity during the week while 27% of the population participate in muscle strengthening activities on at least 2 days per week. (CDC, 2011). Furthermore, 20.6% of U.S. adults (23.4% men and 17.9% women) meet both the aerobic and muscle-strengthening guidelines. This means that the majority of Americans trying to lose or maintain weight will have a positive weight balance due to not meeting the minimum physical activity guidelines.

Weight Gain Buster Solutions
The propensity toward sustained television watching, sleep deprivation, disproportionate alcohol consumption, excessive intake of sugar-sweetened beverages, food consumption of high-caloric density foods, and physical inactivity are clearly indicators of an 'obesogenic lifestyle,' and should be the targets of any behavior change plan for the prevention of weight gain. It should be noted that a person's psychological stress that accompanies any of the above behaviors may indeed exacerbate weight gain, and thus must also be address with the intervention (Montes and Kravitz, 2011). Personal trainers may be best advised to expand their reach training efforts to address all of these areas with clients in order to ensure successful weight management goals.

Troy Purdom M.S. is an Exercise Science doctoral student at the University of New Mexico, Albuquerque. His scholastic interests include sport performance enhancement and nutrient timing. Troy spends his time racing in the regional cycling events and playing recreational sports.

Len Kravitz, PhD, is the program coordinator of exercise science and a researcher at the University of New Mexico, Albuquerque, where he won the Outstanding Teacher of the Year award. He has received the prestigious Can-Fit-Pro Lifetime Achievement Award and American Council on Exercise Fitness Educator of the Year.

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