14 Popular Diets That Have the Worst Long-Term Results

Not all popular diets are as effective as they claim to be. Many of them might have some benefits in the beginning, but have disappointing results in the long-term. If you want to lose weight and keep it off, strategies like eliminating food groups, restricting calories, and not eating enough of one nutrient — and too much of another — aren’t going to help much.

Here are the diets you should stay away from if you want to achieve results that last. Sometimes, the hype doesn’t always align with reality.

1. The military diet

military men walking together

Popular diets like the military diet focus on eating less, but not eating better. | iStock.com/ChrisSupersea

You might know this diet from its alternate names: the navy diet, the army diet, or the ice cream diet. Here’s how it works: For three days, you follow a strict 1,400 calories-per-day meal plan. Foods on this plan range from bread to crackers to vegetables to ice cream. For the remaining four days, you’re encouraged to eat “normally” — no food restrictions — while still keeping your daily calories relatively low. The diet itself only lasts a week, but you can repeat it as many times as you want until you reach your weight loss goals.

The military diet claims you can lose 10 pounds in a week. While you might be able to lose weight eating this way, a lot of that is probably water weight, which you’ll usually regain quickly once you stop restricting calories. Also, diets that restrict calories aren’t sustainable long-term. If you keep at this diet for multiple weeks in a row, your body won’t get the proper nutrition it needs to stay healthy. It’s also extremely low in protein, which means you’ll be much hungrier than usual while following the plan. The hungrier you are, the harder it is to resist junk food cravings.

2. The paleo diet

lots of veggies on a plate

This diet is great if you enjoy buying expensive food and never drinking alcohol ever again. | iStock.com/Lilechka75

On the surface, the paleo diet isn’t all that bad. It promotes eating more healthy fats, grass-fed meats, and fresh produce. Those going paleo are also encouraged to cut out processed foods, refined sugars, and foods high in excess sodium. That’s pretty much where the benefits end, though. You can’t eat grains, dairy products, legumes (beans, peas, and lentils), or potatoes on this diet.

There are several reasons why the paleo diet isn’t the best long-term solution for weight loss or learning to eat healthier. For one thing, it’s expensive: Grass-fed beef, for example, costs almost $3 more per pound than conventional beef. For another, it completely eliminates foods rich in protein, dietary fiber, and B vitamins. Potatoes, beans, oatmeal, brown rice, and quinoa are all excellent sources of these nutrients, but you can’t eat any of them when you’re following these strict guidelines. You can go without these foods, sure, but only if you’re willing to spend more to do so.

3. The Dukan diet

woman stepping on the scale

Getting most of your nutrition from one type of food usually isn’t the best idea. | iStock.com/Rostislav_Sedlacek

This diet is based on the belief that eating mostly meat leads to faster weight loss. Eating more protein does make you feel fuller, but it’s not the only source of nutrition important for weight loss — or health in general. Following the diet, you move through four phases: Two weight loss phases and two maintenance phases. You start by eating mostly lean protein and gradually reintroduce vegetables, some fat, and other low-carb foods back into your meals.

The Dukan diet is a high-protein plan, which by itself wouldn’t be so bad. However, it’s also a low-carb and low-fat diet. According to Mayo Clinic, packing on the protein and restricting carbs can lead to headaches and digestive problems due to insufficient fiber and other vitamins and minerals. The first two phases can result in weight loss, but even when you’re allowed to eat a variety of foods again during the final two phases, foods high in complex carbs and healthy fats still aren’t encouraged. Research hasn’t looked at the outcomes of this diet over the long term, but right now, there just doesn’t seem to be many benefits to eating mostly meat and basically cutting out everything else.

4. The low-fat diet

veggies in a pan for stir-fry

Beware of low-fat labels. | iStock.com/Mizina

When weight-loss plans are praised for the wrong reasons, they’re just as misleading as fad diets. Diets low in fat are the perfect example. Low-fat guidelines can promote healthy eating in many people who try them, but not necessarily because they’re low in fat. In moderation, fat is not the enemy. Unsaturated fat is heart-healthy and may even help to lower levels of bad cholesterol, for example.

Low-fat diets discourage processed foods high in saturated fat, but the suggested alternatives are often high in sodium and added sugars. Don’t be fooled into buying and eating unhealthy foods like breakfast cereals, desserts, and other junk foods because they have a “low fat” label. These foods would normally taste like cardboard, so guess what manufacturers add to them to make them taste good? Sugar. No thanks.

5. The HCG diet

woman in a doctor's outfit holding a syringe

You’ve been scammed. | iStock.com/scyther5

The HCG diet claims human chorionic gonadotropin, a hormone produced at high levels in early pregnancy, causes rapid weight loss. This diet has been around since the 1950s, so researchers have had plenty of time to actually study this one. One study, and many before it, found that HCG is not in any way linked to weight loss. People lose weight with this method because it’s considered a very low-calorie diet — WebMD explains you’re limited to 500 calories a day.

By now, HCG not prescribed by a doctor is illegal. So any synthetic HCG you buy from diet programs doesn’t actually contain the hormone, making it completely useless and a total lie. Being the victim of a diet scam is the only result you’ll get from this.

6. Fasting diets

hungry woman with nothing on her plate

Not eating is stressful — literally. | iStock.com/AnaBGD

Fasting for 12 hours before surgery or blood tests isn’t a huge deal. Many people go that long without eating between breakfast and dinner without even trying. Not eating anything for longer than that can do more than make you uncomfortably hungry, though. According to a study in Psychosomatic Medicine, very low-calorie diets — anything less than 800 calories per day — actually increase your stress hormone levels. So if you thought cutting back on junk food alone was stressful enough, imagine how not eating anything at all would make you feel. Intentionally fasting for the purpose of weight loss is also a behavior associated with some types of eating disorders. And, it may even trigger your body to enter “starvation mode,” during which you burn fewer calories. It’s probably best not to use fasting to tip the numbers on the scale in your favor, even in the short term.

7. The lunar diet

the moon in the sky

The werewolf diet won’t produce the results it promises. | iStock.com/vovan13

The moon diet. The werewolf diet. Whatever you want to call it, it goes like this: For 24 hours, during a full moon, you consume only water and juice. During the waning moon, you eat a “balanced diet” while drinking eight glasses of water daily. With the new moon comes 24 more hours of eliminating solid food, plus drinking detox tea. The lunar diet finishes out with the waxing moon, which comes with a completely new set of strict rules: no eating after 6 p.m., as well as restricting calories as much as possible.

There’s no evidence to support any of the lunar diet’s claims. Humans are made up of plenty of water, but there isn’t any credible research detailing how the moon affects the fluids in our bodies. Eating or not eating at a certain time of day doesn’t guarantee weight loss. Any weight you might lose on diets like this is probably water weight. Most importantly, it doesn’t teach you anything about eating healthy, which is the best strategy for sticking to any diet long term.

8. The Whole30 diet

fresh produce with salmon on a plate

Some diets don’t work simply because they’re unrealistic. | iStock.com/Elena_Danileiko

The Whole30 diet is a 30-day meal plan very similar to the paleo diet. You eat a variety of organic meats and produce while avoiding dairy and grains and focusing on home-cooked meals and snacks. At a glance, this seems like a reasonable diet to try. Yet it suffers from the same inconveniences as the paleo diet.

Whole30 isn’t a diet that mirrors reality as most of us know it. You can’t go out to eat or enjoy yourself at a bar. If you bring your lunch to work, it has to be homemade. Everything you eat, you have to buy and prepare yourself. While this might be an ideal way to eat, it’s not practical for everyone. Like paleo, it can get expensive. Also, while you might lose weight eating plenty of healthy carbs and protein, the diet only lasts 30 days. You might not be able to resist the temptation to drive straight to the nearest McDonald’s if cooking is a major struggle for you. In terms of training yourself to eat fewer processed foods, it’s a great start. Other than that, benefits seem minimal.

9. The Biggest Loser diet

asparagus in a bundle

Popular diets like this promote fast weight loss, which isn’t sustainable. | iStock.com/Vima

Losing massive amounts of weight on TV is the inspiration many people hope to find when trying to convince themselves to drop a pant size or two. However, you don’t see what happens to someone who lost hundreds of pounds on The Biggest Loser after they return to normal life. Scientific American reported a number of the show’s participants had gained weight and suffered slower metabolisms within six years of losing weight. The study in question was small, but it does bring up important considerations about how quickly you should expect to lose weight that stays off.

The Biggest Loser diet can be effective for weight loss whether you have 20 or 100 pounds to lose. However, whether or not you can keep the weight off for months, or even years, depends on how quickly you lose it. Fast weight loss has consequences — mainly losing lean muscle mass and, in some cases, slowing your metabolism. You might be able to lose all the weight you need to on this diet. You just can’t expect to lose as much weight in the exact same time frame as the contestants on the show. Healthy, lasting weight loss is slow — but it’s worth it.

10. The body reset diet

Popular diets like cleanses and detox diets don't do what they claim to do.

Can a smoothie eliminate all the toxins from your body? | iStock.com/Lilechka75

The body reset diet is a 15-day “detox.” Over the first five days of the diet you would consume only smoothies. Over the following 10 days, solid foods are gradually introduced until the three, five-day phases are over. Similar to Whole30, you don’t get to drink or eat out for the duration of the diet. While smoothies sound like an appealing health food, you’ll grow tired of them quickly, making this diet hard to stick to. The major reason this diet won’t deliver the results it promises is because it’s a cleanse. Cleanses and detox diets claim to rid your body of junk and unwanted toxins. That’s not how biology works. Your liver and kidneys are mostly responsible for ridding your body of toxins. They do this naturally — a smoothie doesn’t have that kind of power.

11. The alkaline diet

a bowl of mixed nuts

Your blood pH has nothing to do with food. | iStock.com/margouillatphotos

The alkaline diet is based on the idea that eating acidic foods changes the pH balance in your blood, and therefore should be avoided. Blood pH hovers around 7.4, which is neutral on the pH scale (neither acidic nor “alkaline,” or basic). Major changes in blood pH mean your lungs and kidneys aren’t maintaining blood pH as they should be. If you ever get to that point, something is critically wrong with you.

This is likely where the idea food influences blood pH comes from, since your kidneys do filter toxins out of your blood. While the foods you eat do influence the pH of your urine, food doesn’t have any effect on the pH of your blood. This diet isn’t based on any credible evidence. Eating acidic foods isn’t going to throw your blood pH off balance. The alkaline diet also eliminates many foods and beverages you’re probably used to eating. If you’re not prepared to basically become a vegetarian for the sake of weight loss, you won’t last long on this diet.

12. The gluten-free diet

You probably don't need to go gluten-free.

A gluten-free brownie is still a brownie. | iStock.com/Photology1971

Gluten, found in wheat, barley, and rye products, is a protein only harmful to 1% of the population. You’ll find gluten in breads, cereals, pastas, and more. Many people go gluten-free because they believe it promotes healthy eating and weight loss. There isn’t any evidence to support this idea, though. People with celiac disease must follow a gluten-free diet to relieve symptoms of an allergic reaction to gluten. However, going on a gluten-free diet when you don’t have to won’t help you lose weight or avoid processed foods. It doesn’t matter if it’s gluten-free: Processed food will still probably kill you eventually.

13. The Bulletproof diet

fair trade coffee on a shelf

The Bulletproof diet promises weight loss, but it’s not as easy as you think. | Getty Images/Mario Tama

According to the Bulletproof diet, processed foods are “toxic” and whole foods are “bulletproof.” Conceptually, that’s not wrong. However, this diet claims to have the power to make you lose weight by cutting out wheat and dairy and encouraging meat, produce, and bulletproof coffee. The diet’s biggest downfall, surprisingly, is that it discourages people from counting calories. While you can lose weight without doing this, on this diet, not counting calories can easily lead to overeating and weight gain. Calorie counting, when you’re eliminating as many foods as you are on this diet, can help you keep tabs on how much you’re eating — and drinking. Since you have to alter your calorie intake to lose weight, it doesn’t make sense that this diet expects you to consume bulletproof coffee, which adds 350 additional calories to your day per cup.

14. The apple cider vinegar diet

apple cider vinegar next to whole apples

Too much of a good thing is not all that good after all. | iStock.com/YelenaYemchuk

Here’s a general rule to follow when examining health benefits: Just because it’s good doesn’t mean more is better. Apple cider vinegar is a perfect example of this misconception. Taking things to the extreme, people go on apple cider vinegar detox diets. On an apple cider vinegar detox, you drink only apple cider vinegar and water. You also follow a strict diet of mostly produce for three days.

Apple cider vinegar has plenty of health benefits. It promotes healthy digestion, increases feelings of fullness, and can lower your blood pressure. It’s not a miracle weight loss serum, though, especially not as part of a “detox.” If you want to put it on your salad, fine. Too much apple cider vinegar over long periods of time, though, could cause dangerously low potassium and tooth damage if you take diets like this too far.

How to choose a diet that actually works

a big cut of steak with potatoes

Choose a diet you can actually stick to. | iStock.com/Lisovskaya

While these diets aren’t your best options if you want long-term results, there are plenty that science has proven worthy. The Mediterranean diet, for example, promotes eating a variety of plant-based foods, as well as consuming healthy fats and getting plenty of exercise. The DASH diet is less of a diet and more like a healthy eating guide everyone should follow as closely as possible. Weight Watchers is also an effective diet plan for weight loss, rewarding both healthy eating choices and regular exercise. If you want results, choose a diet that promotes healthy eating and promises weight loss — but not more than a pound or two per week. The diet that works for you is the one you should stick to. Just be realistic about your expectations, whichever one you choose.