# The Smoothie Diet in Fall: Does It Still Work? > Cold weather shifts appetite and motivation. Here is what seasonal-nutrition research says about running a smoothie-based plan once fall temperatures drop. Canonical: https://thefitforty.com/articles/the-smoothie-diet-in-fall-does-a-warm-weather-program-still/ Published: 2026-09-30 --- You started The Smoothie Diet over the summer, or you are thinking about starting it now, and the calendar is working against your enthusiasm. Cold, ice-heavy smoothies made total sense in July. Now that mornings are cooler and you want something warm in your hands before you want anything blended, it is fair to wonder whether the whole approach still holds up once fall settles in. > **The short answer:** A smoothie-based program does not stop working because the temperature drops. What actually changes in fall and winter is your appetite and your motivation, and both of those shift for reasons that have nothing to do with which diet plan you picked. ## Does a Smoothie-Based Program Still Work Once It Gets Cold? The strongest direct evidence here does not come from The Smoothie Diet itself. It comes from a comparable format tested under realistic winter conditions. A small pilot randomized controlled study of 22 overweight adults put a shake-based intermittent energy-restriction program up against a habitual-diet control group across the toughest stretch of the year for eating habits: the six weeks from Thanksgiving through New Year. Over the 52-day study, the program group achieved a small but statistically significant weight loss from baseline, about 1.3 kg, while the control group's weight did not change significantly; the difference between the two groups was not statistically significant. Compliance ran at 98%, and no severe adverse events were reported ([Journal of Nutritional Science](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6436006/), 2019). That trial did not test The Smoothie Diet specifically; it used its own program design, and we are not claiming otherwise. But it is a real test of whether a shake- or smoothie-style plan can hold up through the exact window when eating habits usually go sideways. The result argues against the idea that a cold-weather smoothie plan is inherently mismatched to the season. Format is not the obstacle. What people struggle with in winter is something else entirely, and that is worth separating out. ## Why Does Your Appetite Feel Stronger in Fall and Winter? If you have noticed you are hungrier in October than you were in July, that is not a failure of willpower, and it is not a sign the plan stopped working. Research is still emerging, but colder weather appears to affect appetite in a few ways. When it gets cold, your body has to work harder to maintain its core temperature, which burns more energy and can lead to feeling hungry. Darker days can lower serotonin, which can increase hunger and reduce the satisfaction you feel after eating. And eating itself produces diet-induced thermogenesis, a rise in energy output after a meal that warms your body up ([OhioHealth](https://blog.ohiohealth.com/why-are-you-hungrier-when-its-cold-outside/)). Your appetite is not broken in the fall. Your body is responding to colder, darker days in ways it doesn't in the middle of summer, and that shift shows up no matter which meal plan sits in front of you. If a smoothie that kept you satisfied in August leaves you scanning the pantry an hour later in November, that is the expected physiological pattern, not evidence you are doing something wrong. ## Is It Harder to Stay Consistent With a Smoothie Plan in Colder Months? At the population level, the honest answer leans toward yes. A longitudinal observational study found that food intake, activity, and body weight follow a seasonal pattern: calorie intake was higher in fall than in spring, physical activity was lowest in winter, and body weight peaked in winter, though the authors note the size of these changes was generally small ([European Journal of Clinical Nutrition](https://pmc.ncbi.nlm.nih.gov/articles/PMC1428793/), 2006). That is the backdrop most people are quietly working against every fall, regardless of which program they use. It is worth holding that finding next to the winter-holiday pilot study above, though. With a defined structure, that trial's participants still averaged 98% compliance through the same season when the general population tends to drift toward higher intake and lower activity. Read together, the two studies do not say fall makes adherence impossible. They suggest unstructured eating drifts in cold weather, while a defined plan gives you something concrete to follow at exactly the point when your own hunger signals are working against you. ## What This Means for How You Approach Fall None of this is a reason to treat September or October as a bad time to start, and it is not a reason to feel behind if you are already partway through the program when the weather turns. It is a reason to expect the mechanics of the season to work against you a little, and to plan your expectations around that instead of being surprised by it partway through. If you are also navigating the hormonal shifts of perimenopause or menopause, a stronger fall appetite can feel like one more unpredictable variable stacked on an already unpredictable pattern. The research above was not conducted on this life stage specifically, but the underlying mechanisms it describes, the extra energy your body spends staying warm and the effect of darker days on serotonin, are general physiological responses, not something tied to any one demographic or any one program's formula. Expecting hunger to show up louder in November than it did in July is realistic. Treating that louder hunger signal as proof the plan has failed is not supported by anything in the research reviewed here. If there is a practical shift for fall, it sits in expectation rather than execution. The 21-day structure itself does not change. What changes is the understanding that willpower is not the variable doing the heavy lifting in cold months; your body's response to cold and seasonal motivation patterns are. A defined plan is what the winter-holiday pilot study showed people could stick with through the hardest stretch of the year, rather than something to set aside until the weather cooperates. ## Should You Swap Smoothies for Warm Meals During Winter? We looked for cold-weather or seasonal modification guidance in The Smoothie Diet's official materials and did not find any. As documented, the program is presented as a fixed 21-day structure regardless of season, with no temperature-based adjustment built into the recipes ([Smoothie Diet official site](https://www.smoothiediet.com/how-to-lose-weight-with-smoothies/), accessed 2026-09). That is a real gap if you genuinely do not want a cold drink in December, and we are not going to invent an official workaround the program itself does not document. The research above is about appetite in cold weather, not about the temperature of your food, so the discomfort of an iced smoothie in January is a preference issue, not proof that the nutritional approach behind it stops functioning once the temperature drops. If drinking something cold every day genuinely feels wrong to you in winter, that is useful information about your own adherence, separate from whether the program can work in principle. ## Is There a Better Season to Start a Program Like This? If the real question is when to start rather than whether to start, seasonal search-trend research offers a useful signal. An infodemiological study of Google search data from six English-speaking countries found that searches for weight loss peak in spring and sit at their lowest point in autumn, pointing to a seasonal rhythm in public interest that exists independent of any specific program's effectiveness ([PubMed](https://pubmed.ncbi.nlm.nih.gov/32349915/), 2020). Read plainly, that suggests fall is when collective interest in starting something like this is at its lowest point of the year, not because programs stop working in autumn, but because collective interest itself dips. If you are starting a smoothie-based plan in September or October, you are working against that low point rather than with it. That is not a reason to wait until spring. It is a reason to expect the first couple of weeks to take more deliberate effort than they might if you started the same plan in spring, when search interest in weight loss peaks. This is also where the winter-holiday pilot study becomes more useful than the search-trend data on its own. The winter holidays are exactly the stretch that pilot tested, and a defined program still produced 98% compliance through it. The takeaway is not that fall motivation is a myth. It is that a structured plan may help carry you through it when motivation alone runs low, which is arguably more useful to know before a fall start than after one. ## Where This Leaves You Nothing in the research reviewed here points to a smoothie-based program becoming ineffective once the leaves turn. What it does show is that your appetite can run a little hotter in cold weather for physiological reasons that have nothing to do with the program, that collective interest in weight loss is at its seasonal low in fall rather than spring, and that The Smoothie Diet's official materials do not offer season-specific adjustments if that is something you were hoping to find. None of that is a reason to abandon the idea. It is a reason to go in expecting a slightly harder adjustment period than a summer start, and to treat stronger fall appetite as biology rather than a verdict on your discipline. If you are still deciding whether this program fits your situation at all, it is worth comparing it against other structured options before you pick a season to begin. [The Smoothie Diet vs Old School New Body After 40](/articles/smoothie-diet-vs-old-school-new-body-after-40/) lays out how a smoothie-based approach differs from a strength-training program in daily structure. [The Smoothie Diet vs DIY Meal Prep After 40](/articles/smoothie-diet-vs-diy-meal-prep-after-40/) is worth a look if the appeal was never the smoothies specifically, just having a plan you do not have to build yourself. And if you have not read the full breakdown yet, [The Smoothie Diet Review](/articles/the-smoothie-diet-review/) covers what the 21-day structure actually includes, which is worth knowing before you decide when on the calendar to start it.