Thanksgiving and weight gain: trivial or not, and riskier for the overweight?

Originally published on 11.23.2010. No additional research has been done since. Tomorrow I will post the subsequent article that examined research on the entire holiday period.

Is the Thanksgiving holiday a prime time for weight gain?  Is it riskier for people already overweight or currently dieting?  Unfortunately, I am only able to find 2 studies that specifically examine the effect Thanksgiving has on weight gain, and both have limitations that make definite conclusions difficult.  I summarize those 2 studies below.  For the quick and dirty summary, scroll to the bottom.  There are several other studies that have looked at the entire holiday season, as well as Christmas by itself on weight.  I will describe these studies in upcoming separate posts.

Hull et al. (1) studied 94 (44 male, 50 female) undergraduate and graduate students from the University of Oklahoma to see if weight gain over the Thanksgiving holiday was significant.  The week prior to the break, body weight, height, and waist and hip circumferences were measured.  After the holiday these were assessed once more; the average time between the first and second assessment was 13 +/- 3 days (minimum 5 and maximum 17 days).  75% of the participants were Caucasian, 10% Hispanic, 6% Native American, 5% African American, and 4% Asian.  The subjects were also grouped by: undergraduates (66), graduates (28), normal BMI (60), and overweight/obese BMI (34).

For all 94 subjects, bodyweight increased on average by 0.5 kg (1.1 lbs.).  Males averaged a 0.5 kg increase while females gained 0.4 kg.  Graduates gained on average 0.8 kg, and undergraduates 0.4 kg.  Interestingly, the already overweight/obese BMI (> or = to 25 kg/m^2) category gained the most at 1 kg, compared to the normal BMI (less than 25 kg/m^2) category who only gained 0.2 kg.  Here is the table they provide:

Strangely, the change in weight circumference decreased across the board, while the change in hip circumference increased.  I don’t know what to make of those results and the authors didn’t comment about them in the discussion.  Here they are:

A big limitation of this study is the fact that the subjects knew the goal of the study was to monitor changes in body weight over the Thanksgiving holiday, so they may have altered their behaviors before, during, and/or after the assessment period.

Of course, there is significant individual variation as well.  Some subjects gained significantly, some lost.  Here is a link to the scatter plot that shows this variance.

An older study by Klesges et al. (2) on 65 college students (31 men, 34 women)

These subjects were also grouped by relative weight: 37 “normal weight” and 28 “overweight,” (which as far as I can tell are arbitrary classifications) as well as by “restraint” (dieting): 31 “high restrained” and 34 “unrestrained” from the Revised Restraint Scale  (Note: I see that the generalizability of this classification has been challenged, though I have not thoroughly researched this area).

The subjects’ heights and weights were taken, then they were instructed to record everything they consumed over an 8-day period in a food diary (from Tuesday prior to Thanksgiving to the Tuesday after).  After the holiday, they completed another Restraint questionnaire and their heights and weights were again taken (strange that they needed height twice!).

Total calories and 9 nutrients were estimated with the computer program DINE. Results for average total calories per day were separated into the 2 days prior to Thanksgiving, the 4-day holiday weekend, and the Monday and Tuesday after.  As one would expect, intake increased per day over the Thanksgiving period, by nearly 300 kcal per day over the 2 days prior.  For normal weight subjects, dieters appeared to attempt to compensate for the additional calories by reducing intake after the holiday compared to prior, whereas the non-dieters returned to normal eating habits.  Overweight non-dieters however did not appear to significantly alter total intake throughout the experiment, whereas overweight dieters, who averaged less total intake than normal-weight dieters prior to the holiday, maintained their restriction of total intake after the holiday.  It is easier to visualize:

In general, males consumed more total calories, though female dieters reduced total calorie intake much more sharply after the holiday than males.  See the following graph:

Weight data was not graphed, but they noted that there was no correlation between increased intake and weight gain in this study, but rather strangely, dieting was associated with weight gain (I would guess a rapid restoration of glycogen/water weight from an acute large meal would cause this in dieters).

Summary/Conclusions

The first limitation of these studies is that they both are on college student populations, who have different eating habits than the average person.  They also gain weight at a different rate than the average person.  In young adults, the average weight gain referenced from (1) is about 0.2 to 0.8 kg per year.  This may not seem like much, but accumulation each year can add up quickly.  Though the “freshman 15″ is a myth, the authors from (1) note recent studies that have found weight increases per year of 1.3 kg to 2.5 kg in college populations.  So it is possible that weight increases in college populations (which was 0.5 kg on average from study 1) are magnified, and weight gain from Thanksgiving in non-college populations are less.  Based on the results from other studies on the entire holiday season (which I will review in a future post), this may be the case.  Thanksgiving is a short holiday and one might assume that acute overindulgence isn’t anything to worry about.  However, based on the results of the first study discussed here as well as the other holiday studies, and other research that suggests holiday weight is generally not lost, a significant amount of the average yearly weight gain can be explained by weight gain during this time of the year.

So in study 1, is the increase in weight kept after the Thanksgiving period?  These studies do not specifically address this.  The other holiday research adds some perspective, and it would seem that it is, at least some of it.

So why do the overweight/obese seem more susceptible to weight gain?  Without further study of things such as total calories, activity levels (and non exercise activity thermogenesis assessment), potential social confounders, and weight distribution, many questions are left unanswered.  Some research also suggests that (some) overweight/obese people are more likely to overeat in settings with abundant food- than non-overweight/obese for a number of reasons.  It seems that this may be the case with holidays.  It should also be noted that dieters from the 2nd study seem to be susceptible to “binging,” making holidays a potentially stressful and difficult time for weight maintenance.  My next post on this will explore this as well.

Thanksgiving and other holidays seem to be risk factors for weight gain.  An overabundance of foods and beverages along with strong cultural and social influences make it especially important to be mindful of how much you are consuming.  Be careful this week!

References

1. Hull HR, Radley D, Dinger MK, & Fields DA (2006). The effect of the Thanksgiving holiday on weight gain. Nutrition journal, 5 PMID: 17118202

2. Klesges RC, Klem ML, & Bene CR (1989). Effects of dietary restraint, obesity, and gender on holiday eating behavior and weight gain. Journal of abnormal psychology, 98 (4), 499-503 PMID: 2592685