Adaptation to Intermittent Ramadan Fasting Takes Time, but Eventually Mood, Fatigue, and the Quality of Life Improve

No, it wasn't a button like this which made the subjects happy.

It took some time, yeah, but after a few weeks the participants, students of the Hannover Medical School, where the trial was conducted actually felt better, not - as the scientists who conducted this Ramadan fasting study had expected - worse than without their religious fasting.

But let's not go too fast, here. The subjects had volunteered to participate in the study and were non-randomly assigned to a fasting (FG) and a non-fasting (NFG) group (according to their individual plans | Nugraha. 2016).
To be eligible into the FG, participants had to: (1) be healthy, (2) be older than 18 years of age, (3) intend to fast the whole month of Ramadan, (4) have fasted during Ramadan at least once before, (5) understand the German or English language. For the NFG, all subjects had to meet the criteria of the FG, except that they would not be fasting. Furthermore (and that's IMHO a pity) The NFG participants were assessed only at T1 and T3. That's in contrast to their peers in FG, where participants were assessed at four different points: one week before Ramadan (T1), mid-Ramadan (T2), the last days of Ramadan (T3), and one week after Ramadan (T4).

Figure 1: While the perceived fatigue of the subjects skyrocketed in the early phase of the Ramadan fast, it dropped during the latter phase and achieved an all-time low in the post-Ramadan week (this peak is missing from the fatigue severity score that kept declining continuously | not shown in Figure 1). The subjects' overall mental health, on the other hand, improved, but without a significant treatment effect due to religious fasting (Nugraha. 2016).

Unfortunately, the lower "resolution" in the NFG group, makes it impossible to directly compare the mood and QoL progression over time.
What the data I've plotted for your in Figure 1 still tells you is that the subject's perceived level of fatigue skyrocketed in the initial phase of Ramadan fasting and improved to sub-control levels at the end and one week after Ramadan fasting. At the same time their mental health scores improved, albeit not significantly.

Figure 2: Mood and sleepiness show a similar pattern over the course of the trial (Nugraha. 2016).

Similar trends were observed for the subjects' mood and their sleepiness scores, which were  was measured by using the Epworth Sleepiness Scale (ESS), a self-administered questionnaire with 8 questions that are rated on a 4-point scale (0–3) to yield a score ranging from 0 to 24, with higher scores indicating that person's average propensity of daytime sleepiness increased.

Table 1: Body composition before, during, and after Ramadan (Nugraha. 2016).

The effects on the subject's body composition are significantly less obvious. There were no significant differences in all parameters at both T1 and T3 when comparing FG and NFG. Plus: the way the figures "evolved" make me question the accuracy of the InBody machine (InBody 230; Model MW160, Korea) the scientists used.
References:

• Aksungar, Fehime Benli, et al. "Comparison of intermittent fasting versus caloric restriction in obese subjects: A two year follow-up." The journal of nutrition, health & aging (2016): 1-5.
• Fond, Guillaume, et al. "Fasting in mood disorders: neurobiology and effectiveness. A review of the literature." Psychiatry research 209.3 (2013): 253-258.
• Mattson, Mark P., Valter D. Longo, and Michelle Harvie. "Impact of Intermittent Fasting on Health and Disease Processes." Ageing Research Reviews (2016).
• Michalsen, Andreas, et al. "Hunger and mood during extended fasting are dependent on the GNB3 C825T polymorphism." Annals of Nutrition and Metabolism 54.3 (2009): 184-188.
• Michalsen, Andreas. "Prolonged fasting as a method of mood enhancement in chronic pain syndromes: a review of clinical evidence and mechanisms." Current pain and headache reports 14.2 (2010): 80-87.
• Nugraha, et al. "Effect of Ramadan fasting on fatigue, mood, sleepiness, and health-related quality of life of healthy young men in summer time in Germany: A prospective controlled study."Appetite - Available online 24 December 2016 | In Press, Accepted Manuscript 
• Solianik, Rima, et al. "Effect of 48 h Fasting on Autonomic Function, Brain Activity, Cognition, and Mood in Amateur Weight Lifters." BioMed Research International 2016 (2016).
• Uher, Ivan, et al. "Intermittent fasting and its influence on health." Physical Activity Review 4 (2016): 184-191.
• Watkins, Ellen, and Lucy Serpell. "The psychological effects of short-term fasting in healthy women." Frontiers in Nutrition 3 (2016).