These diet foods could be making you fat. Or at least not helping you lose weight.
It is estimated that 45 million Americans go on a diet every year, spending $33 billion on weight loss products annually, according to the Boston Medical Center. And yet, nearly three quarters of Americans are overweight or obese, according to the National Center for Health Statistics.
This disconnect could be down to the way we are dieting.
"The diet industry makes billions of dollars by making people think that 'healthy' diets have to include products like protein bars, low-fat and low-calorie products, diet beverages, and other highly-processed foods and drinks," nutritionist Jillian Kubala told Newsweek.
But "low calorie" does not always mean "healthy." To start with, highly processed foods typically contain high levels of artificial colors, preservatives, sodium and other additives. "In combination, these ingredients have been linked to health issues like cancer, cardiovascular disease, and all-cause mortality," Sarah Garone, a registered nutritionist and author of the blog A Love Letter to Food, previously told Newsweek.
Highly processed, or "ultra-processed," foods may also set back your weight loss.
"There's a big difference between non-fat and zero-sugar whole foods and heavily processed fat-free and sugar-free foods," Samantha Cassetty, an expert in plant-forward nutrition and co-author of the book Sugar Shock, told Newsweek. "Think of how quickly you can eat 100 calories of fat-free, sugar-free candies, cookies, chips, or other heavily processed fare compared to how quickly you could eat 100 calories' worth of lentils, which are also fat-free and sugar-free. And the heavily processed foods won't fill you up as well as whole foods, so you're more likely to overeat them."
Cassetty pointed to a study in 2019, published in the journal Cell Metabolism, in which 20 participants were asked to monitor how their body weights responded to a diet based on highly ultra-processed foods compared to one based on whole foods.
"Everyone went on both arms of the study for two weeks," Cassetty said. "The diets were closely matched for calories, protein, fat, carbs, fiber, and sugar, and people were allowed to eat as much or little as they wanted.
"Interestingly, people ate faster and more on the ultra-processed diet, gaining an average of two pounds over two weeks. The very same people lost an average of two pounds on the whole foods diet. So, even if you're eating something with no fat or sugar, when food is heavily processed, it's probably easier to overeat, putting you in a calorie surplus. And it may be undermining other metabolic processes, too."
"I also think sugar- and fat-free snack foods have a diet halo, so there's a belief that they're freebies, or at least that they're not having a dramatic effect on your weight. But I find that many people are less satisfied with diet snacks, and if you aren't mentally happy with your food, there's a strong chance you'll keep eating until you reach that point, which makes it harder to lose weight."
These low-calorie ultra-processed foods may also be loaded with artificial sweeteners.
"Study findings suggest that diets high in artificial sweeteners may actually increase body weight and the risk of type 2 diabetes," Kubala said. "A 2017 systematic review and meta-analysis of randomized controlled trials and prospective cohort studies that included data on 405,907 people found that the consumption of artificial sweeteners over a median of ten years was associated with an increase in weight, body mass index (BMI), and waist circumference as well as an elevated risk of high blood sugar levels, obesity, type 2 diabetes, metabolic syndrome, and heart disease."
The WHO has also recently announced that one of the most popular artificial sweeteners, aspartame, is "possibly carcinogenic" to humans.
However, artificial sweeteners do give consumers sweet-tasting options while allowing them to reduce their sugar intake. "Many ["healthy"] products, such as flavored yogurts and pre-made smoothies and protein shakes, can contain high amounts of added sugar, an ingredient that should be limited as much as possible for overall health," Kubala said. "Some pre-made smoothies stocked on grocery shelves can contain over 25 grams (which equates to 6.25 teaspoons) of added sugar in just one serving."
Let's have a look at which foods might fall into this category:
- Flavored yogurts—these often contain significant quantities of added sugar or artificial sweeteners.
- Diet sodas—these usually contain artificial sweeteners.
- Shop bought smoothies—these often contain high amounts of added sugar.
- Protein bars—these are often ultra-processed and may contain artificial sweeteners.
- Plant-based meat substitutes—these are often highly processed to mimic the texture and taste of meat.
So what should you eat to lose weight healthily?
"When looking at labels, scan the ingredient list for sugar substitutes, sugar (which is fat-free), and refined grains (like enriched wheat flour)," Cassetty said. "These are red flags that a food is heavily processed, and it's helpful to eat these foods less often.
"A better idea is to focus on whole foods that will fill you up and make you feel your best and to learn how to enjoy snacks you love mindfully–whether they have sugar and fat or not. An eating pattern that will help promote weight loss is rich in plant foods, including vegetables, fruits, whole grains, beans and legumes, and nuts and seeds. Reducing refined carbs and swapping them for fiber-rich whole food carbs, such as whole grains and starchy veggies, is also helpful.
"These foods supply a mix of heart-healthy fats, fiber, antioxidants, phytonutrients, and vitamins and minerals that promote health, and they're also filling. And plant foods improve your gut health, which plays a role in nutrient absorption and weight loss."
However, if you do have the odd low-fat yogurt or sugary smoothie, you shouldn't be too hard on yourself.
"Food isn't meant to be feared, it's meant to be enjoyed and fuel your body with the nutrients it needs to function optimally and promote physical and mental health," Kubala said. "In my opinion, eating patterns that involve slow yet consistent dietary changes are most effective for shifting the way you view food. These small changes can add up over time and shift your entire dietary pattern into a more nutritious, well-rounded way of eating."
Cassetty, too, emphasized the importance of sustainable, healthy weight loss: "Remember that healthy weight loss isn't about thinness. It's about reaching a weight where your blood pressure, blood sugar, cholesterol, and other health markers are in an appropriate zone, you're eating a variety of plant foods (though you don't have to be exclusively plant-based), and enjoying a full life, including social activities that revolve around food. The idea is to develop a sustainable lifestyle, so you're thinking less about dieting and making space for other things you value."
