On March 15, 2020, the Dutch Government implemented COVID-19 lockdown measures. Although self-quarantine and social-distancing measures were implemented, restrictions were less severe compared to several other countries. The aim of this study was to assess changes in eating behavior and food purchases among a representative adult sample in the Netherlands (n = 1030), five weeks into lockdown. The results show that most participants did not change their eating behaviors (83.0%) or food purchases (73.3%). However, socio-demographic differences were observed among those that reported changes during lockdown. For example, participants with overweight (OR = 2.26, 95%CI = 1.24–4.11) and obesity (OR = 4.21, 95%CI = 2.13–8.32) were more likely to indicate to eat unhealthier during lockdown compared to participants with a healthy weight. Those with a high educational level (OR = 2.25, 95%-CI = 1.03–4.93) were also more likely to indicate to eat unhealthier during lockdown compared to those with a low educational level. Older participants were more likely to indicate to experience no differences in their eating behaviors compared to those of younger age, who were more likely to indicate that they ate healthier (OR = 1.03, 95%CI = 1.01–1.04) as well as unhealthier (OR = 1.04, 95%CI = 1.02–1.06) during lockdown. Participants with obesity were more likely to indicate to purchase more chips/snacks (OR = 2.79, 95%CI = 1.43–5.45) and more nonalcoholic beverages (OR = 2.74, 95%CI = 1.36–5.50) during lockdown in comparison with those with a healthy weight. Of those that used meal delivery services before, 174 (29.5%) indicated to use meal delivery services more frequently during lockdown. Although the results confirm the persistence of dietary routines, profound socio-demographic differences were observed for those that did report changes. Especially for individuals with overweight and obesity, the lockdown has taken its toll on healthy dietary choices. Further research should unravel underlying mechanisms for these observations.