5 'diet' foods that can cause weight gain

By Liz Meszaros, MDLinx
Published September 4, 2019

Key Takeaways

If you're on a diet, the supermarkets seem to be chock-full of foods that promise to help you. But, a word of caution is necessary, and should be heeded before you run down the aisles, grabbing low-fat and reduced-sugar options willy-nilly.

Some of these foods that are low-fat, low-sugar, and even low-carb options are not all they're cracked up to be, and may actually sabotage your efforts to lose weight.

Here's a list of five "diet" foods that can actually be counterproductive to weight loss.

Protein shakes and smoothies

Protein shakes and smoothies are having a moment, and, indeed, they are convenient ways to lose weight and get some vitamins and extra protein. They can decrease hunger and appetite, and make you feel fuller for longer, so you consume fewer calories.

But while some shakes and smoothies are healthy and contain extra nutrition, beware: some premade smoothies can have up to 55 g of sugar and almost 400 calories per serving.

The key with anything premade is to carefully read the nutrition label and be aware of what you are drinking. Try to avoid ingredients like carrageenan, heavy metals (which occur naturally in things like rice protein powders and even cocoa powders), and sugar substitutes.

Healthier alternatives: A safer bet for your diet would be to forego anything premade and drink only what you have mixed at home. That way, you control the sugar and extra ingredients, and know exactly what is in the shake or smoothie—with no surprise ingredients like sugar or extra calories, or even preservatives or fillers.

Low-fat, flavored yogurt

Yogurt has many clinically proven health benefits. It can be a good source of calcium and protein, enhance healthy gut bacteria, and even protect against osteoporosis and help your digestion.

But, when eating yogurt, it might be good idea to stick to unflavored, full-fat options. Low-fat products usually contain added sugar to compensate for the flavor loss that occurs when fat is removed. In fact, eating high-fat dairy products is usually a better choice, based on results from a study involving over 8,000 women who became obese or overweight. Researchers found that those who ate more high-fat dairy products actually gained less weight than those who consumed low-fat products.

Healthier alternatives: Stick to regular, unflavored yogurts. Greek yogurts are especially satisfying.

Alternative sweeteners

If you're trying to avoid white sugar in your diet, the good news is that you have a wide array of alternative sweeteners to choose from. The bad news is that these products may not be as healthy as they are touted to be.

Agave, for example, has more calories than regular white sugar, and is high in fructose. Fructose has a lower glycemic index than glucose, and won't cause quick spikes in blood sugar or insulin levels. But, fructose may contribute to insulin resistance and fat accumulation. And, agave is much higher in calories than regular sugar.

The same is true for coconut sugar, another sugar alternative. This sugar consists of the dehydrated sap of the coconut palm tree's flower. Coconut sugar retains some of the nutrients found in the coconut palm, including iron, zinc, calcium, and potassium, as well as some polyphenols, antioxidants, and inulin—a fiber that slows glucose absorption. Like agave, it has a lower glycemic index than table sugar.

But, again, the sticking point of coconut sugar is its fructose content. While labels may claim that it's fructose-free, coconut sugar is comprised of 70% to 80% sucrose—half of which is fructose. Essentially, the nutritional value is outweighed by its high fructose content.

Healthier alternatives: Honey, maple syrup, molasses, and even raw sugar are some 100% natural alternatives to sugar.


A traditional breakfast and snack food, granola is perhaps the granddaddy of healthy food options. Typically made of rolled oats, honey, nuts, seeds, and sweeteners (including brown sugar) that is baked to a toasted, golden brown consistency, granola offers a range of nutritious ingredients. The oats have high fiber and iron contents; the nuts add heart-healthy unsaturated fats and protein; and the seeds can be a source of essential amino acids and minerals, including calcium, zinc, copper, and magnesium.

But, the kicker is that granola can have a very high calorie content, and contain oils and sugars that are not healthy. Again, read the nutritional label carefully.

Healthier alternatives: Try to choose a granola that has no more than 6 g of sugar per serving. Or, make your own granola at home. Simply bake a mixture of oats, nuts, coconut oil, and whatever dried fruit you prefer at a low temperature.

Diet sodas

Considering that regular soda can contain an obscene amount of sugar—a 12-oz can of Coca-Cola, for example, has 39 g of sugar—diet soda, with no sugar, can seem like the perfect alternative.

But, more and more studies have shown that it is not.

For example, in a recent study that recruited over 2,000 people, it was found that drinking diet soda was associated with weight gain rather than weight loss. Further, hypertension and high blood glucose levels were more likely to be found in participants who consumed diet sodas compared with those who did not.

Diet soda has also been shown to have a negative effect on gut bacteria, which can increase the risk for developing diabetes and other metabolic disorders.

Healthier alternatives: Water is always a safe go-to when you are thirsty. Green tea is another great choice, and is delicious hot or cold. Or you can try kombucha, which contains significantly less sugar than most fruit juices, has both antibacterial and antifungal properties, and may reduce your risks of heart disease, type 2 diabetes, and even cancer.

The bottom line for your dieting success is, choose healthy, whole foods that you can prepare yourself rather than those that are labeled "low-fat." Choose whole foods that have nutritious amounts of proteins and healthy fats, and few sugars.

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