It’s been suspected for quite some time that minor weight gain over the holidays is one of the root causes of the obesity problem in the US, and may even be responsible for the slow increase in weight that most American adults experience as they grow older. Surveys of Americans find that most of us actually gain only 1 pound of weight in a normal holiday season (the 6 weeks between Thanksgiving and New Year’s Day). But if you gain 1 pound every year between the ages of 25 and 65, it’s pretty easy to see what’s going to happen to your weight as you age. More concerning studies indicate that obese people gain more than 1 pound during this same time period, and that some people gain as much as 5 pounds during the holidays! A new study from the University of Bath in England (where they have very similar holiday celebrations to those in the US) demonstrates in rather shocking detail just what happens when we overeat for a week and slack off on our exercise programs. And, let’s be honest here, who hasn’t done that over the holidays at one time or another?
The subjects in this study were 26 men in their mid-20s who engaged in 30 minutes or more of structured, vigorous-intensity exercise, at least 3 times a week. This hearty bunch was divided into two groups. The researchers planned for both groups to have the same caloric surplus during the study. For a week, both of the groups decreased their exercise and daily physical activity to less than 4000 steps per day, as measured on a pedometer or wearable step counter (10,000 steps per day is considered a healthy level). They also ate at least 50% more calories than they were accustomed to – setting them up for weight gain (of course, this is not unlike what happens to many of us during the holiday season; though this is hopefully an exaggerated version of what most of us experience!). And, since they usually ate around 3200 calories a day – appropriate for men of this age and activity level – this 50% increase means they had a very high caloric intake, an impressive 4800 calories every day!
One of the groups was designated to be the added exercise group. While they decreased their regular daily exercise and workouts, in addition to eating 50% more than their usual calorie intake just as the control group did, they also ran on a treadmill for 45 minutes a day. But, because this exercise would’ve reduced their caloric surplus relative to the non-exercise group, the researchers boosted their daily calories by an additional 25%, increasing their total (daily) caloric intake to a whopping 75% of their norm! According to the researchers, both of the groups ate predominantly carbohydrates for their excess calories. We’re thinking they didn’t gorge themselves on whole grains and starchy vegetables either! We’re thinking more along the lines of sweet holiday desserts like mince pie (about 475 calories and 80 g carbs per serving), or a sugary muffin from the bakery (about 500 calories and 70 grams of carbs). Again, not unlike what so many of us experience during the holiday season! These committed research participants also had blood tests, body composition analyses, glucose tolerance tests, and even biopsies of their abdominal fat in order to determine the effects of overeating on the expression of various metabolic genes.
It will likely not come as a surprise to learn that both groups gained weight! However, the control group gained nearly 6 pounds, while the added exercise group gained only 3.5 pounds. The control group also had more than double the addition to waist circumference relative to the added exercise group! And, when researchers looked at the biochemistry of the subjects, they found even more alarming results. The control group had higher insulin levels in their blood (a known stimulant of many cancers) than the added exercise group, and the rise in insulin levels that occurred after they were given a test drink of glucose doubled relative to their original results, a sign that the body is working harder to deal with its sugar load. We’d expect this, since they weren’t nearly active enough to burn off all those calories! However, the added exercise group didn’t experience any change in the insulin reaction to glucose drinks.
Another important dimension of the way the body handles sugars is insulin sensitivity. When we have normal insulin sensitivity, sugars can easily be transported into our cells to be used for fuel. When our insulin sensitivity drops, sugars – along with insulin – keep circulating in the bloodstream. Both of them can be harmful to our health, and this is particularly true for cancer patients. Would you be surprised to learn that the control group had worse insulin sensitivity after their week of overeating than the added exercise group? We weren’t! The exercise in the added exercise group helped stabilize insulin sensitivity, in spite of all the added calories. Studying the metabolism of the two groups in more detail also demonstrated that, in the control group, extra sugar was destined to wind up as more fat in the body through a process called lipogenesis. Lipogenesis didn’t increase, though, in the added exercise group.
The researchers also studied the tissue derived from abdominal fat samples to see what changes in gene activity resulted from the overeating and exercise deficit. One thing that happened was that a gene connected to fat-burning, PDK4, decreased in the control group, indicating that their bodies were using sugars for fuel, rather than burning off fat tissue – certainly not something most of us want to have happen! The gene AMPK, which also increases fat-burning, was lowered in both groups, but more so in the control group.
So, the added exercise protected these volunteer overeaters in several ways: by maintaining insulin response and insulin sensitivity, stopping lipogenesis, and maintaining fat-burning. It’s a clear message that exercising on the same days as you are overeating will help keep you in reasonably good metabolic condition, even if you do gain some weight. And, it should be mentioned that this isn’t the first time we’ve seen the potential benefits of exercise when study participants were overeating. Previous research found that after 3 days of overeating without exercise, a single 60-minute bout of exercise brought the body’s insulin response at least partially back towards normal.
With this University of Bath study, we know in more detail what happens to many, if not most of us, over the holidays. A time when overeating is fairly common (but hopefully not 50% or 75% more than our normal calorie intake!), and we’re less likely to stick to a regular exercise regimen. Clearly, it can be a metabolic disaster! But, this study suggests there’s something we can do about this “disaster.” First, try not to overeat! Remember, it’s the first few bites of a wonderful holiday meal that are the most satisfying. You really don’t have to overindulge to enjoy yourself. And, even in the midst of all the preparations and celebrations for the holidays, take some time for your health. Get on that treadmill or exercise bike, or, weather permitting, go out for a long and brisk walk. If you can’t manage this on the actual holiday itself – and we know that Christmas Day or New Year’s Eve may not be the ideal time to rush out to the gym or even fit in a brisk walk – start exercising as soon afterwards as you can.
With this in mind, we wish you all a happy and healthy holiday season, and much good health in the coming year!
For more information on The Block Center for Integrative Cancer Treatment, call (847) 230-9107 or visit www.BlockMD.com