So many of my article ideas come from social media. “You Can Lose Up To 5 Kg in 3 Days With Potatoes & Yogurt!” the headline on the shared post declared. Well, naturally that got my attention. I write a lot about my own efforts to lose weight, so both food science and food woo are a topic of interest for me. So, gritting my teeth, I clicked the link. The new page informed me that:
The main ingredient of the potato diet, as you can conclude is the potato. This diet also includes low-fat yogurt.
Potatoes will keep you full for a longer period of time and that way you will consume less calories. While you are on this diet you will need to eat only cooked potatoes and to drink yogurt but only the one with low fat.
Well, bonus points for being exactly what it says on the label, I guess. Let’s go right ahead and jump right into the claims of the… article? Can I dignify it with a word like “article”? The parasitic text attached to the clickbait. How’s that?
Claims One and Two
The parasitic text continues:
The feeling of satiety is achieved when the potato starch starts swelling in our stomach Remember that you need to eat only baked potatoes and not French fries. In potatoes there is a high content of fiber which will also speed up the metabolism and that will help to lose weight fast.
I may have mentioned this before, but I’m not an organic chemist or a doctor (medical or other). I’m a stockbroker. Still, this sounded… wrong. So, I spent a whole lot of time trying to figure out a good web search that would shed some light on this. And I’ll be honest: I couldn’t find anything supporting the idea that potato starch “swells” in the stomach. I did learn quite a bit about starch, though, and one of the first things I learned is that starch comes in three distinct “flavors”:
- Rapidly digestible starch, which “is found in high amounts in starchy foods cooked by moist heat, such as bread and potatoes.It is measured chemically as the starch, which is converted to the constituent glucose molecules in 20 min of enzyme digestion.”
- Slowly digestible starch, which is expected to be completely digested in the small intestine. This includes starches found in cereals, and the starches found in potatoes either before they are cooked or after they are cooled.
- Resistant starch, which is starch that escapes digestion in the small intestine, and which is partially digested in the large intestine before being expelled from the body.
I also learned that there is at least one study reporting cooked potatoes average between 2.5% and 4% resistant starch, and over 90% rapidly digestible starch—although this falls to around 60% rapidly digestible and 40% slowly digestible starch if you allow it to cool. Which means that, far from reducing feelings of hunger, potato starch—the bulk of the potato—will be fully digested between 20 minutes and two hours after consumption.
As far as the claim that dietary fiber will “also speed up the metabolism and that will help to lose weight fast,” I couldn’t find any actual evidence that it “speeds up the metabolism” (if there is any, please let me know). There is some evidence, though, that increasing your dietary fiber intake will help reduce weight. According to the abstract for “Increasing total fiber intake reduces risk of weight and fat gains in women,” the authors write that “[f]or each 1 g increase in total fiber consumed [over a 20 month period], weight decreased by 0.25 kg (P = 0.0061) and fat decreased by 0.25 percentage point (P = 0.0052).” So, yes, the fiber in potato would theoretically help reduce weight.
Of course, so would the dietary fiber in anything else. Potato isn’t a magic superfood fat-destroying bullet.
Claims Three and Four
100 g potato contains only 75 calories, which is less than a glass of orange juice. On the other hand, yogurt regulates the digestive system, which removes excess fluids, toxins and other harmful substances from your body.
Claim number three is easily checked. According to the USDA, the “average” potato contains 77 calories (dietary calories or kcal, to be technical) per 100 grams. I won’t quibble with their “75 calories” statement, because they can range from 69 calories per 100 grams for white potatoes to 79 calories per 100 grams for russet potatoes and because I’m not interested in picking nits. Instead, let’s give them this one and move on to claim four:
Yogurt regulates the digestive system, which removes excess fluids, toxins and other harmful substances from your body.
That, I believe, is the longest collection of non-specific woo words strung together in a sentence that I’ve personally had to type out. I mean, where do you start? The digestive system is regulated by, broadly speaking, the autonomic nervous system through a number of receptors that detect the presence of different chemicals and pressures within the alimentary canal. Nowhere could I find any description of the impact yogurt might have on that portion of the nervous system, beyond the effect that any food would have.
Oh, and then there’s the magic word “toxins.” And by “magic” I mean “gibberish.” But, to sum up, the digestive system doesn’t do much to remove toxic substances from the body. It’s actually a primary vector for toxic substances to enter the body, and then the liver and kidneys has to do the heavy lifting removing the toxic substances. Some may be excreted as solid waste through the colon, but that’s not a primary function of the digestive system.
All right, so the claims are questionable. Does it work?
I’m glad you asked. Here, I’ll sum up the diet for you:
- On day one, you eat a boiled potato for breakfast and drink a glass of lowfat yogurt. Lunch is two boiled potatoes and one glass of yogurt, and then dinner is two glasses of yogurt.
- On day two, you drink a glass of yogurt for breakfast. Lunch is two boiled potatoes and one glass of yogurt, and then you skip dinner.
- On day three, you eat a boiled potato for breakfast. Lunch is one boiled potato and one glass of yogurt. Dinner is one glass of yogurt.
- Note: If you are exercising regularly or you have some kind of health problems then this diet is not recommended for you. Remember that this diet is only three days, so do not use it for a longer period of time.
Yep. But, since you asked, let’s do some analysis. We’ll be generous, and assume that each potato is a large russet potato. That gives us 292 calories per potato. The size of a “glass” of yogurt is never defined in the “article,” so let’s assume we’re talking about eight ounces of low-fat plain yogurt per glass, for 143 calories. That means that you’re consuming the following:
- Day One: 1,448 calories
- Day Two: 870 calories
- Day Three: 870 calories
Yeah. No kidding. There’s a thing called Basal Metabolic Rate, which is calculated in several different ways, but is the energy required to maintain your weight if all you are doing is staying alive and maintaining your weight. Here’s a link to a calculator so you can see what your BMR is. Mine, according to that calculator, is 2,656.74 calories—a figure that matches up, more or less, with what my FitBit provides. The calculator states that to maintain your weight you should then adjust your BMR based on your activity level:
- If you are sedentary (little or no exercise): Calorie-Calculation = BMR x 1.2
- If you are lightly active (light exercise/sports 1-3 days/week): Calorie-Calculation = BMR x 1.375
- If you are moderately active (moderate exercise/sports 3-5 days/week): Calorie-Calculation = BMR x 1.55
- If you are very active (hard exercise/sports 6-7 days a week): Calorie-Calculation = BMR x 1.725
- If you are extra active (very hard exercise/sports & physical job or 2x training): Calorie-Calculation = BMR x 1.9
The warning I quoted above states that I shouldn’t use this diet if I’m exercising, so let’s assume I will be sedentary for three days. So, to maintain my weight as I work at my desk and walk from home to car to desk and back, I should consume 3,188 calories. Over the course of three hungry days, I’ll have burned 6,376 calories. Now, a common (but possibly incorrect) rule of thumb is that you have to burn 3,500 calories more than you take in to shed a pound of fat. So I’ll be almost a full order of magnitude short of the 5 kg this diet promises that I’ll burn. (I’d have lost 1.8 pounds, and 5 kg is 11 pounds.
In other words, the diet is not only scientifically illiterate, but it also doesn’t even work as promised.
I think we knew that.
I’m sure you did. I pretty well knew it, going into this article. But that’s not the point. This is the point:
The “potato and yogurt” diet is just one example of a general class of “miracle diets” that ask you to do “one simple thing” and promise you the moon. This particular diet has the virtue of not actually trying to sell you anything—the article doesn’t even have links to online stores selling you superfood potatoes or superfood yogurt or any nonsense like that. But so many of these miracle diets will also try to hook you into purchasing pills and powders and tinctures of serpens oleum, sometimes for more than a $100 a crack, on a repeating automatic purchase. They prey on frustration and appeal to the urge to get something for nothing, and they give you only rubbish and an empty checkbook. If you’re lucky. If you’re unlucky, they give you debt and serious health issues.
If you want to lose weight, don’t fall for mass marketing schemes through direct mail or internet clickbait. The only “one simple trick” you need, unless you have genuine medical issues, is this: talk to your doctor, eat a variety of foods in moderation, and exercise.
Further Reading on Starch: