The holiday season often leads to resolutions focused on weight loss. However, as Natalie Thompson, a certified nutrition specialist and wellness coach at UR Medicine’s Center for Employee Wellness, points out, attempting to diet in winter might mean working against your body's natural inclinations. While "diet" can refer to a specific eating plan involving calorie counting, it also broadly describes the foods a population consumes. Thompson emphasizes that "restrictive diets are very ‘yes’ or ‘no,’ and they often fail because of the lack of choice." Diets that disregard the body's natural rhythms can also be unsuccessful, as exemplified by New Year’s resolution diets. Although the beginning of the year is a good time to reflect on lifestyle habits and make healthy changes, winter may not be the ideal season for significant weight loss.
The Body's Winter Cravings
Thompson explains that "in the colder weather, we’re more inclined toward sleeping and resting for longer periods. Our bodies crave more calorically dense foods, or rich foods." Instead of fighting these cravings, Thompson suggests finding ways to create "healthy, nourishing, calorically balanced meals to suit those warm, comforting, cozy cravings" during the winter months. As the weather warms, our bodies naturally gravitate towards lighter foods.
Regardless of the season, it's important to include protein, whole grains, and fruits and vegetables in every meal. Address unhealthy snacking habits by checking in with yourself about why you’re eating. Thompson notes, "We’re not always intentional with food. When we turn to food for any reason, without knowing that’s what we’re doing, that’s when we get lost in the food."
The Science of Cold and Fat Burning
While the idea of shivering through winter to lose weight may seem unappealing, research suggests that cold exposure can trigger physiological changes that promote fat burning. Humans and other mammals shiver to stay warm, but cold also stimulates the growth of fat cells that burn fuel, rather than store it. Studies have shown that keeping humans indoors at 61 to 63 degrees Fahrenheit without allowing them to bundle up can lead to weight loss.
Fat-burning fat cells have power plants called mitochondria that spin inefficiently, causing them to burn more energy and generate heat. This accelerated fat burning is triggered by the activation of a protein called uncoupling protein 1 (UCP1) within the mitochondria. Cells containing UCP1, known as brown fat or beige fat, are capable of heat generation and fat burning.
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The Immune System's Role in Fat Conversion
Building on previous research, Chawla’s team discovered that the signaling molecules, called interleukin 4 and interleukin 13, activate cells known as macrophages, which in turn drive the fat conversion.
In 2011, Chawla's team reported in Nature that cold activates part of the immune system, and specifically activates interleukin 4 in fat. The new discovery is surprising because this control mechanism for fat burning bypasses components of the autonomic nervous system that govern many physiological adaptations. In comparison to the nervous system, the immune pathway might be more easily manipulated to increase energy expenditure, Chawla said.
The Potential and Limitations of Brown Fat
Although researchers like Chawla believe that the potential to exploit brown fat for weight loss is significant, the amount of individual variation in brown fat reserves and the potential to generate more brown fat remains unclear. "We don’t know what the dynamic range is," Chawla said.
Muscle, Heat, and Sarcolipin
Muthu Periasamy, PhD, a professor at Sanford Burnham Prebys Medical Discovery Institute (SBP) at Lake Nona, studies how muscle burns calories to generate heat. Because we need to keep our bodies at around 98 degrees Fahrenheit, being in a cold environment makes us burn more calories to generate enough heat. To lose weight by cold exposure, you’d have to be outside most of the winter or have your thermostat set to something like 40 degrees Fahrenheit.
Periasamy's research focuses on a protein called sarcolipin, which regulates calcium movement inside muscle cells. More sarcolipin means more calcium transport, which generates more heat. Mice lacking sarcolipin were unable to stay warm when exposed to cold for several hours, even though they had brown fat. Any treatment would have to be combined with exercise.
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Weather's Influence on Weight Loss Behavior
Research indicates that people were less likely to report attempting to lose weight, including dieting and exercising, when temperatures fell below 68°F (20°C). Conversely, when the daily maximum temperature rose above 77°F (25°C), people were more likely to report trying to lose weight, consuming the recommended servings of fruits and vegetables, and spending more time exercising. According to co-author Brandyn F. Churchill, assistant professor of public administration and policy at American University, “What surprised us is the degree to which the weather was a factor in shifting behavior related to weight loss".
Overweight and obese individuals were least likely to pursue weight loss when it was cold and most likely to do so when it was warm. Despite these behavioral shifts, the study found no evidence that they had any measurable impact on respondents’ body mass index (BMI). "For BMI to change, you need consistent habits,” Srivastava explains. “We captured short-term deviations in behavior based on whether it’s really hot or really cold."
Practical Tips for Winter Wellness
Winter doesn’t have to be an obstacle to your health. Here’s some advice from the experts.
Avoid Overly Restrictive Diets
Setting strict diet rules, especially during special occasions, might seem like a way to prevent your weight loss journey from derailing. However, research suggests that rules can sometimes backfire. An Associate Professor and Eating Disorder Specialist from the University of Minnesota says that although the winter holidays can be a challenging time for healthy eating, an overly intense focus on diet “rules” can taint one’s relationship with food and their own wellbeing. It can even lead to more overeating. Ultimately, extreme healthy eating can become a psychological concern.
Stay Active, Even Indoors
Part of your fitness and weight loss journey is staying active. But, in the cooler months, many people find this difficult. Luckily, even small amounts of exercise are beneficial, according to experts from Harvard Health. Researchers concluded that 15 minutes of moderate activity and as little as eight minutes of vigorous activity each day can reduce your risk of early death.
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The Centers for Disease Control and Prevention offers the following ideas for getting in extra activity during cold-weather periods: walk a few laps at the shopping center on your next store run, take the stairs at every opportunity, park farther away instead of relentlessly hunting for a nearby parking spot, or go for a group walk when your friends or family visit you. Whatever you decide to do, keeping the body moving is essential for offsetting the extra calories that often come with winter eating.
Embrace the Cold (Safely)
Though you might find it more difficult to exercise in the winter, the good news is that your body might be working in your favor when it’s cold out. That means, the exercise you do manage to accomplish might have bonus benefits. Research shared by the National Institutes of Health has shown that cold weather can activate “brown fat” in our bodies, a type of fat that burns calories to generate heat. This means that exercising in the cold can potentially boost calorie burn, making winter workouts even more effective.