This study confirms that eating food away from home (FAFH) adversely affects dietary intake. By looking at changes within individuals’ dietary intake over two days, thus controlling for self-selection issues, we find that FAFH causes increased caloric intake and reduced diet quality. Our estimates on the effect of specific meals show that lunch and dinner consumed away from home have the largest effect on total daily caloric intake, but that breakfast has the largest negative effect on total diet quality. In particular, eating breakfast away from home decreases intake of fruit, whole grains and dairy and increases the percent of calories from saturated fats and solid fats, alcohol and added sugar. Eating lunch and dinner away from home also reduce diet quality, affecting similar dietary components, with dinner away from home also reducing vegetable intake. Unlike past studies based on correlation analyses, this study shows how FAFH can have a causal impact on weight gain.