. 2023 Sep 28;15(19):4201. doi: 10.3390/nu15194201

Table 1.

General characteristics of the studies included in the systematic review.

Author, Year, and Country	Study Duration	Number of Participants	Age, Sex,	BMI, Prevalence of Overweight/Obesity	Date of Measurements	Mean Weight Changes ± SD
Helander EE et al. (2016); USA, Germany, and Japan [10]	Thanksgiving (USA), Christmas (Germany), Golden Week (Japan); 1 year (2–6 months)	2924 (1781 USA, 760 Germany, 383 Japan);	USA: 42.4 years, 34% F. Germany 42.9 years, 34% F Japan: 41.6 years, 26% F.	USA: 24% obese; Germany:19% obese; Japan: 11% obese	1 August 2012–31 July 2013	Significant increases in weight pre- and post-Christmas across all three countries (0.4% in the USA; 0.6% in Germany; 0.5% in Japan). Significant weight increases occurred over Thanksgiving in the USA (0.2%), Golden Week in Japan (0.3%), and Easter in Germany (0.2%). Annual weights increased by 0.7% (0.6 kg) in the USA and 1.0% (0.8 kg) in Germany over the Christmas-New Year period, and 0.7% (0.5 kg) in Japan over Golden Week.
Cooper and Tokar, 2016, USA [11]	Between the months of March and August.	122	Mean age 32.2 ± 13.0 years 65% women (n = 79) and 35% men (n = 43),	57 normal weight—46.7%, 46 overweight—37.7%, 10 obese—15.6%, average BMI 25.8 ± 0.3 kg/m²	1 week before vacation, 1 week after vacation and 6 weeks after vacation	People with normal weight accumulating 0.28 ± 0.13 kg, while overweight people gained 0.39 ± 0.14 kg, and obese people gained 0.48 ± 0.27 kg
Bhutaniet al., 2020, Madison Metropolitan area [12]	15 September–15 January	23	Age 21–50 years	BMI: 30–39.9 kg/m²	15–30 September to 9–25 November (three visits) 9–25 November to 4–15 January (three visits)	A decrease of 0.86 kg during the pre-holiday period vs. an increase of 0.41 kg during the holiday period. Non-significant change with estimated energy intake in the expected direction (+80 kcal/day in holiday period vs. pre-holiday period)
Viñuela, et al., 2023, University of Castilla-La Mancha [13]	23 December–13 January	67, 10 men (14.9%) and 57 women (85.1%)	Mean age 19.00 ± 1.63 years for the males and 20.61 ± 4.33 year	BMI measurement (21.7 ± 3.1) and the second (21.9 ±3.1) and between the second and third (21.7 ± 3.9), observing a decrease	Four measurements: 23 December, 30 December, 6 January, 13 January	Over the Christmas holiday period, the overall weight tended to increase, from an initial weight of 59.6 ± 10.7 kg to 60.2 ± 10.6 kg at the end of the period, whereas 1 week after returning to university, the mean weight was 59.6 ± 9.9 kg. An increase between the first BMI measurement (21.7 ± 3.1) and the second (21.9 ± 3.1) and between the second and third (21.7 ± 3.9), observing a decrease in the return to university (22.6 ± 5.9) to values that were almost the same as at the start of the period but with a slight increase.
Olson, et al., 2020, USA [14]	November 2018–January 2019	683	54.6 years [SD: 13.2]	69% female, 93% white, BMI: 26.9 kg/m² [SD: 5.5]	November 2018, January 2019	Participants gained 0.66 kg (SD: 1.85) from pre- to post-holiday and reported using an average of 12/18 strategies. More strategies were associated with less weight gain (F [1, 670] = 4.28). Daily self-weighing and prioritizing food choices were individually associated with less weight gain.
Mason et al., 2018, Birmingham, UK [15]	November 2016–February 2017	272 (136 were randomized to a brief behavioral intervention and 136 to a leaflet on healthy living)	Mean age: 43.9 years	BMI of ≥20 kg/m² 78% women, 22% men	Baseline assessments were conducted in November and December, with follow-up assessments in January and February (4–8 weeks after baseline)	The mean weight change was −0.13 kg (95% confidence interval −0.4 to 0.15) in the intervention group and 0.37 kg (0.12 to 0.62) in the comparator group. The adjusted mean difference in weight (intervention− comparator) was −0.49 kg (95% confidence interval −0.85 to −0.13). The odds ratio for gaining no more than 0.5 kg was nonsignificant.
Kaviani, et al., 2019, USA [16]	November–April	111	18–65 years	BMI ≥ 18.5 kg/m²	V1: before Thanksgiving, V2:after New Year’s Day, and the follow-up visit V3: 14 weeks after V2	There was no change in weight with DSW + GF, whereas the control group gained weight from v1 to v2 (−0.13 ± 0.27 kg vs. 2.65 ± 0.33 kg), respectively. In the control group, weight change was similar between individuals with overweight or obesity (OW/OB) vs. individuals with normal weight (2.71 ± 0.48 kg vs. 2.62 ± 0.43 kg, not significant, respectively). For DSW + GF, individuals with OW/OB lost weight, whereas those with normal weight-maintained weight during the holidays (−1.46 ± 0.62 kg vs. 0.33 ± 0.27 kg, respectively). The control group lost weight during the follow-up (−1.14 ± 0.43 kg; v2 to v3) but retained 57% of weight gain; therefore, weight gain from v1 to v3 was significant (1.51 ± 0.39 kg).
Wilson et al., 2019, USA [17]	2015–2016	239 (100 employees in year 1 (2015–16) and 139 employees in Year 2. 36 repeated participants	47.1 years (+10.46)	Mean weight: 196.7 lb/89.2 kg. Approximately 90% of the participants were female. A majority of respondents were African-American (71%), followed by white (24%) and others (5%)	End of October to mid-January (weight was measured every two weeks during the program (at 2, 4, 6, and 8 weeks) as part of the intervention)	During the program, participants lost a significant amount of weight (from 196.7 lb/89.2 kg to 192.3 lb/87.2 kg), losing weight at each weigh-in. To examine weight maintenance between programs, data were analyzed from the 36 repeat participants (who participated in both years of the program). Participants, on average lost 6.9 lb (3.1 kg) in Year 1, gained 8.7 lb (4.0 kg) between the programs, and lost 4.3 lb (2.0 kg) in Year 2 of the program resulting in a net loss of 2.5 lb (1.1 kg)
Stevenson, et al., 2013 [18]	57 ± 0.5 days (2013)	148	Age 18–65 years	48 males and 100 females, mean body mass index of 25.1 ± 0.5 kg/m²	Mid-November (visit 1) and early January (visit 2)	Participants showed significant increases in BW (0.78 ± 0.1 kg), BF% (0.5 ± 0.2%,) systolic blood pressure (SBP; 2.3 ± 1.2 mm Hg), and diastolic blood pressure (1.8 ± 0.8 mm Hg. Obese participants (35.2 ± 0.8 kg/m²) showed a greater increase in BF% compared with normal weight participants (21.7 ± 0.2 kg/m²) and a trend vs. overweight participant (26.8 ± 0.3 kg/m²). Exercise (4.8 ± 0.6 h per week) did not protect against holiday weight gain and was not a significant predictor for changes in BW or BF%.
Ramirez-Jimenez, et al., 2020, Barcelona, Spain [19]	November–January	38 (TRAIN group, n = 16, HOLID group, n= 22)	57 ± 8 years	BMI 32 ± 5 kg/m² and metabolic syndrome	20 December (visit 1) and 10 January (visit 2)	HOLID group increased body weight (91.3 ± 13.0 to 92.0 ± 13.4 kg), mean arterial pressure (94.0 ± 10.6 to 97.1 ± 8.9 mmHg, blood insulin (10.2 ± 3.8 to 12.5 ± 5.4 µIU·mL⁻¹) and HOMA (3.2 ± 1.3 to 4.1 ± 2.3). In contrast, TRAIN prevented those disarrangements and reduced total (170.6 ± 30.6 to 161.3 ± 31.3 mg·dL⁻¹) and low-density lipoprotein cholesterol (LDL-C, 104.8 ± 26.1 to 95.6 ± 21.7 mg·dL⁻¹.