The first chapter exploits a natural experiment to provide causal evidence of the effects of changes in the price of CSD on obesity prevalence. Additionally, this paper tests the hypothesis that obesity prevalence in developing countries might be especially sensitive to changes in the price of CSD due to poor access to safe drinking water. The main argument is that individuals should be more willing to substitute away potentially contaminated water than clean water. Hence, if the price of CSD decreases, individuals with access to potentially contaminated water should be more willing to substitute their consumption of CSD for water than individuals with access to clean water. From this prediction it follows that these individuals should experience a higher increase in weight, since water has no calories, while most CSD and other beverages do. Moreover, individuals with access to potentially contaminated water should experience decreases in their probability of contracting diarrheal diseases, since diarrheal diseases are (at least in part) generated by the consumption of contaminated water. I find that a 10% decrease in the price of CSD increases (Body Mass Index) BMI of adult women of childbearing age by 0.12 units (0.5%), and obesity rate by 0.9 percentage points (8.5%). These effects are explained by an elasticity of demand of 1.3 units in young families (and of 1.0 in the general population) with no substitution effect on milk, non-carbonated soft drinks or alcoholic beverages. I do find complementary effects on food prepared outside the home but consumed at home. I find no effect on the number of times the families eat outside home. Thus, the increase in weight outcomes cannot be explained by the proliferation of fast food restaurants. The effects are significantly higher for families without access to piped water in their homes; the effects on BMI and obesity rates are more than twice as high in absolute terms than those for women with piped water at home. Moreover, I find that a 10% decrease in the price of CSD reduces severe diarrhea prevalence by 16% in women without access to piped water in their homes. The second chaper exploits an experiment in Northern Morocco to analyze the effect of households' connection to drinking water network on childhood weight. I find that the treatment successfully increased access to water but there is no clear evidence of whether the treatment increased the quality of the water. I also find that 5 months after the connection to the water network, the likelihood of a child being obese was 6% in the treatment group versus 13% in the control group, and the difference was statistically significant. I also find that children in the treatment group had a BMI-for-age 0.17 standard deviations lower than the control group, although this difference was not significant. I find no effect on thinness or malnutrition. Finally, I find indirect evidence that obesity likelihood decreases because children drink more water, substituting away other caloric beverages and not due to an income effect. The third chapter analyses the effects of in-home access to piped water on the consumption of soft drinks and children dental hygiene and dentist visits. The empirical strategy of this study relies on fixed effects at the household level in the analysis of consumption, and at the cluster level (geographical areas that group 120 households on average) in the analysis of dental hygiene and dentist visits. I find that access to piped water reduces soft drinks consumption by 22% and children belonging to these families increase their probability of brushing their teeth by 5%, while reducing their probability of visiting the dentist by 6%. In the case of the more-educated households, I only find an effect on the probability of brushing their teeth; it increases by 1.6%. My dissertation highlights the disproportionate effect the expansion of CSD consumption can have, and probably is having, on obesity and oral health in developing countries, where access to safe water is limited. Furthermore, this study suggests that taxes on CSD could yield unintended results for developing countries. and that improving access to drinking water could not only reduce diarrheal prevalence but also prevent obesity and improve oral health.