The COVID-19 pandemic had a profound impact on public health and resulted in severe economic and social distress at the global level [1]. Recent research has documented deterioration in dietary habits [21] and lifestyle behaviors during the pandemic [11, 13]. The present study compared the patterns of food and beverage consumption as well as physical activity and smoking before and during the quarantine among 638 Saudis.

We detected a detrimental effect of the COVID-19-related quarantine on dietary habits and practice of physical activity among the responders. A significant change in food and beverage consumption in response to the quarantine was observed, including more frequent consumption of fast food, French fries, and candies and less frequent consumption of fish and sugar-free drinks. That was expected since there was limited access to groceries, food insufficiency in stores, and an interrupted food supply chain during the early waves of the pandemic.

Evidence has documented that junk and processed food provoke inflammation and oxidative stress which increases vulnerability to diseases. While fresh foods are rich in antioxidants which have protective effects [21].

The current study observed a remarkable change in the frequency of consuming fast food; where 6.3 and 6.4% reported having junk food 3–4 and 5–6 times per week before the quarantine; then increased to 20.7% and 10.3% respectively during the quarantine. Though, this happened in spite of the fact that maintaining a healthy diet was highly recommended during this serious pandemic period to support the immune system [22, 23]. To our knowledge, during the precautionary measures taken by the Kingdom, restaurants were not completely closed at any stage. Restaurants were closed only during the curfew time which lasted from March 24th till it was opened completely on May 31st. The observed increase of fast food consumption does not align with the findings of a study conducted in Kuwait [24] which found a significant reduction in the frequency of fast-food consumption as a result of fears regarding the transmission of COVID-19, whether it is from unhygienic practices at restaurants, or the delivery driver or people’s desire to eat healthier during the pandemic. Factors such as unexpected lifestyle changes, lockdown, isolation, anxiety, fear, stress, and depression can predispose to unhealthier food choices [25, 26].

Consistent with our findings, previous studies conducted in Saudi Arabia verified the negative impact of the lockdown on healthy dietary patterns and physical activity [25, 26]. This was not consistent with the findings of Di Renzo et al. (2020) who found a better adherence to healthy types of cooking during the COVID-19 quarantine among the Italian population [27].

Though it was insignificant, we observed an increase in the rate of skipping breakfast among participants during the quarantine. This may be understandable, considering that during the study period, there was a partial lockdown and lengthy restrictions at home, which might have led to staying up late at night and oversleeping during the day. This was consistent with Okada et al. 2021 who found a significant association between late dinner or bedtime snack and skipping breakfast [28]. Increased consumption of candies and sugar was evident in the current study, where the (15%) of participants who used to eat candies 5–6 times/day increased to (19.4%). A similar finding was reported by Scarmozzino and Visioli [29], who found that half of the participants of an Italian sample reported an increase in the consumption of sweet foods during the COVID-19 quarantine. This may be due to the stress and anxiety induced by the enforced quarantine and pandemic waves which might trigger a higher consumption of sugary foods [5, 30, 31].

Regarding other food groups, there were no significant changes in terms of red meat, chicken, type of fat, milk, grains, legumes, and nuts consumption, before and during the quarantine. Meanwhile, the present study revealed a significant improvement in some healthy dietary habits including cooking methods, trimming the fat from meat and chicken, lower use of additional salt, purchasing low-salted food, and a considerable increase in fruit and vegetable intake. However, the total healthy eating index score, was 3.5% significantly higher before, compared to during the quarantine period, indicating its adverse effect on dietary quality.

Obesity and deficiency of Vit E, Vit C, Beta carotene, and antioxidants are potentially associated with impaired immunological responses and more susceptibility to the contagion of infectious diseases [22].

It was expected to find a reduction in the consumption of fresh vital food, accompanied by micronutrient deficiency. Interestingly, the consumption of fresh fruits, vegetables, and water/hot beverages among the study participants significantly increased during the quarantine despite of enormous difficulties in the supply of agricultural products early and amid the pandemic [7].

This favorable behavior might be attributed to the prevalent awareness about being sufficiently hydrated and the benefits of eating fruits and vegetables as sources of vitamins and minerals to combat the risk of infection [32].

Likely, findings of a similar study, reported that the majority of the study population had increased their water intake and more than one-third (37.4%) reported eating healthier food including fruits and vegetables [27]. Comparable to our results, we detected a much higher sweets and junk food intake, which are rich in simple sugar and saturated fatty acids [30]. This explains the significant decline of the healthy dietary index observed during the quarantine.

As for the consumption of fish, it was significantly lower than before the quarantine. Similar findings were also reported among Chinese and Kuwait residents by Zhao et al. (2020) [25] and Husain W et al. (2020) [24]. A possible explanation for this behavior includes fish unavailability due to the closure of the fish markets early in March 2020 according to the precautionary measures taken by the Kingdom Public Health Authority (WAQYA).

Unsurprisingly, the most commonly consumed dietary supplements were: vitamin C, iron with minerals, and vitamin D supplements (15.6%, 12%, 5.3%) as shown in Fig. 4, since they are well-known for their immune-boosting effects [33]. A similar pattern of dietary supplement intake was observed by Bakhsh et al. (2021) in KSA [34].

The current study reported a weight gain of around 1 kg (mean BMI; before 72.7 ± 16.8 to during 73.67 ± 18.9 kg/m2). Similarly, Bakhsh et al. (2021) detected a higher weight gain average of ~ 3–5 kg during the quarantine time [34]. This was also consistent with other studies conducted in Italy and Poland [24, 29, 35].

Obesity causes low-grade inflammatory status, elevates adipokine levels released from adipose tissue, and modulates immunological responses [36]. That may induce metabolic disorders such as insulin-dependent diabetes mellitus (IDDM), dyslipidemia, and hypertension. These immunomodulatory effects in the natural and acquired immunity make the human body more prone to infections, alter the response to antiviral and antimicrobial medication, and reduce the immune response to vaccination [37]. The resulting immunological changes could predispose to an exaggeration of the respiratory COVID viral infections [38].

Consistent with the literature, unhealthy meal patterns, and sedentary lifestyle behaviors are likely associated with weight gain [36, 39]. Moreover, the emotional distress accompanied by being locked at home for months and fears of the novelty and the vast spread of COVID-19 might provoke emotional eating and food cravings [7].

The current study found that 42.6% strongly agreed to reduce their body weight and 34.8% strongly worried about any increase in their weight. A much lower proportion was reported from a population survey in Italy, which indicated that 14% believed that they should lose weight and 34.4% reported elevated hunger sensations during the lockdown [27]. This discrepancy could be attributed to sociocultural norms diversity.

Though the weight gain-related concerns among responders were high as shown in Fig. 3; our analysis detected a significant increase in body weight during the quarantine. Emotional eating, negative changes in eating habits, and declined PA levels could rationalize the observed weight gain. This obesogenic environment might contribute to vulnerability to COVID-19 infection and worsen the prognosis [38].

Considerably, more than two-thirds (69.3%) of the study individuals received COVID-19-related guidelines for prevention and control through social media platforms, which necessities-fostering the role of reliable health resources such as the WHO, health authorities, and scientific periodicals to enhance the population health awareness.

Of note, about 8% (n = 11) of smokers reported that they reduced the frequency of smoking below the amount they used to, and only 3% (n = 4) of them quit smoking during the quarantine period. Consistently, an Italian population survey in 2020 reported that 3.3% of smokers stopped smoking during the early pandemic and their smoking rates decreased by 0.5% [27].

This phenomenon might be explained by the fact that during this period people started working from home and would not expose their households to secondhand smoke. Also, the fear associated with smoking hazards may be a factor, as it increases the susceptibility to respiratory complications and the mortality risks of COVID-19 [2]. This is because tobacco smoking stimulates the angiotensin-converting enzyme type 2 receptors which are potential adhesion localities for novel coronavirus SARS-CoV-2 [40].

Regarding the physical activity level, our results indicated that nearly two-thirds of the study participants were physically inactive; consistent figures were reported by the Saudi national survey among the general population in 2020 [41]. However, the low levels of PA were exacerbated by the restrictive measures related to the pandemic, where there was a significant reduction of mean total PA MET/week compared to the pre-quarantine times. Similar results were detected in other related studies [13, 42].  Our findings are supported by recent evidence from local and international observations showing a universal decline in all physical activity levels during the COVID-19 lengthy measures [13, 26, 43]. Since the quarantine restricted the people’s mobility to go to work, gym, parks, and even practice normal daily chores, the observed reduction of PA was anticipated.

Several limitations are noticed in the present study. First, the use of a self-reported questionnaire which was used due to the specific circumstances of the pandemic, since remote data collection using social networks was more feasible and necessary. Second, all participants were asked to report their daily lifestyle habits before the imposed quarantine, which may be subjected to recall bias. Third, convenience sampling may have led to selection bias, thus a probability sampling technique is required to ensure the generalizability of findings by minimizing the potential for bias. Lastly, this study was also limited by its cross-sectional design, which precludes the investigation of causal relationships.

Despite those limitations, there were some important strength points. To the best of our knowledge, this is the first study that documented the preliminary dietary changes in Saudi Arabia, during the implemented quarantine due to the COVID-19 pandemic. This study has public health implications as it can provide background information to public health agencies. The usage of validated questionnaires for assessing the healthy eating index for adults and physical activity was one of the strong points as well. The design of the online questionnaire used, where the questions about lifestyle practices before and during the COVID-19 lockdown were placed next to each other for better recalling and comparing was also a strength point.