Changes in Diet and Lifestyle and Long-Term Weight Gain in Women and Men:
Within each 4-year period, participants gained an average of 3.35 lb (5th to 95th percentile, −4.1 to 12.4). On the basis of increased daily servings of individual dietary components, 4-year weight change was most strongly associated with the intake of potato chips (1.69 lb), potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), unprocessed red meats (0.95 lb), and processed meats (0.93 lb) and was inversely associated with the intake of vegetables (−0.22 lb), whole grains (−0.37 lb), fruits (−0.49 lb), nuts (−0.57 lb), and yogurt (−0.82 lb) (P≤0.005 for each comparison). Aggregate dietary changes were associated with substantial differences in weight change (3.93 lb across quintiles of dietary change). Other lifestyle factors were also independently associated with weight change (P<0.001), including physical activity (−1.76 lb across quintiles); alcohol use (0.41 lb per drink per day), smoking (new quitters, 5.17 lb; former smokers, 0.14 lb), sleep (more weight gain with <6 or >8 hours of sleep), and television watching (0.31 lb per hour per day).
I took the results when they controlled for other variables and filtered them all so that their p-values were 0.001 or less (in fact, of the ones below only "sweets and desserts" is p-value 0.001, all the others are below that). Nothing too surprising, but the magnitude of effect of french fries was pretty large:
I'm a big believer in not taking any given dietary study as gospel, and really doing a lot of personal self-experimentation in terms of your weight loss or gain. With those caveats in mind I think we can safely say that in the aggregate society would do a lot of good if we could decrease the consumption of soft-drinks and fries. That's the "low hanging fruit." I know many people who have given up soft-drinks, and it doesn't seem like a change which is equivalent to going vegan or vegetarian, where back-sliding is very common.