A new fad diet has hit social media, promising a transformation from couch potato to “Spud Fit.” An Australian man has vowed to eat nothing but potatoes for 365 days in an attempt to lose weight and improve his relationship with food. He calls his nutritional journey “The Year of The Spud.”

Well, based on my knowledge of evidence-based nutrition (and common sense), I think this diet is going to be a dud. Why, you ask? It lacks the basic principals of a successful healthy diet: moderation, balance, and variety.

Moderation: For the record, eating potatoes all day, every day is definitely classified as excess, not moderation. It doesn’t matter if it’s kale, carrots, quinoa, cake or even spinach, nutritionally speaking too much of a good thing is not a good thing.

According to the Dietary Guidelines and MyPlate, each of the five food groups has a unique set of vitamins and minerals that promote balanced nutrition. Because Spud Fit promotes overconsumption of one of the groups and elimination of the other four, some very important nutrients, vitamins, and minerals will be lacking. 

Balance: The creator of Spud Fit has reported weight loss since starting the diet and considers this a mark of success. This is not really a surprise, given that weight loss is still a matter of taking in fewer calories than you burn. Or in more technical terms, weight loss relies on the principle of energy balance.

But although he was eating fewer calories, he was also missing the majority of the nutrients (vitamins, minerals, protein, and fat, to name just a few) our bodies need to stay healthy. So overall I would consider “Spud Fit” a nutritional fail, not a weight loss success.

Variety: Needless to say, Spud Fit does not incorporate any variety. The creator states that he had trouble making healthy food choices, so he found that sticking to one option made it easier. I get it, making decisions is hard. (I have been known to spend an hour trying to decide what outfit to wear.) But when it comes to food, it’s important to incorporate variety to make sure you are getting all the essential vitamins, minerals and macronutrients your body needs.

Potatoes contain some nutrients such as carbohydrates, potassium, fiber, and iron, but they are not great sources of protein and healthy fats. Protein is essential for maintaining almost all body systems—not to mention building and maintaining muscle, promoting weight management, and supporting a healthy immune system—while healthy fats support healthy hair, skin, nails and cognitive function, and they form the protective structures that envelop our body’s cells.

The Spud Fit diet is not a sustainable eating pattern, due to potential serious nutritional deficits and restrictiveness. But most importantly, this diet takes the pleasure out of eating. Eating healthy doesn’t have to be boring, and it’s important to enjoy the foods you are eating in order to develop a healthy relationship with food.

Take-Away Message: When assessing a diet, decide whether it incorporates the principles of moderation, balance, and variety, before you believe the hype.