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7 Weight Loss Diets That Don’t Work

By Franziska Spritzler

Many people want to lose weight quickly.

Not surprisingly, methods that promise fast results are tempting. Unfortunately, many of these are overly restrictive and simply ineffective in the long term (1).

What's more, some are downright dangerous.

Here are seven weight loss "quick fixes" that just don't work.

1. Liquid Diets

Liquid weight loss diets have been around for several decades. They involve replacing all or a portion of your meals with a liquid meal or shake.

Some liquid-based weight loss diets include:

  • The Cambridge Diet: The strictest option of this diet provides 440–550 calories as meal replacements for up to 12 weeks. The original plan was criticized for providing as few as 330 calories daily without being medically supervised (2).
  • Protein-Sparing Modified Fast (PSMF): Under medical supervision, obese patients consume fewer than 800 calories daily for six months. Today's PSMFs are considered safe, whereas earlier versions were linked to deaths (3).
  • Optimist and Medifast: Several options are available. Plans providing fewer than 800 calories per day typically last 26 weeks and require medical supervision.

While people can and do lose weight quickly on very low-calorie liquid diets, weight regain is extremely common (4).

This makes sense, since drinking liquid meals doesn't foster healthy eating habits, which are necessary for successful weight maintenance.

In addition, research suggests that following a liquid-based weight loss plan may lead to disordered eating, such as binge eating or food restriction.

In one 28-week study, obese women were assigned to one of several weight loss strategies. By the end of the study, significantly more binge eating occurred in the liquid meal replacement group (5).

While liquid diets may lead to quick, short-term weight loss, they seem to do more harm than good in the long run.

Summary: Very low-calorie liquid diets can produce short-term weight loss. However, they should be supervised by a medical doctor. Weight regain is very common and disordered eating patterns may develop.

2. "Carb-Blocker" Pills

Carb blockers or starch blockers, are supplements claimed to promote easy weight loss.

They contain extracts from beans that interfere with alpha-amylase, an enzyme that breaks down complex carbs into smaller sugar units that your body can absorb (6).

Complex carbs include grains, potatoes and sweet potatoes. If complex carbs aren't broken down into sugar, their calories can't be absorbed by your body.

However, carb blockers can't completely prevent the digestion and absorption of complex carbs. They only slow down the action of alpha-amylase.

In one study, a starch blocker was found to inhibit more than 96 percent of amylase, yet it only prevented 7 percent of carbs from being absorbed (7).

This suggests that if you took a carb blocker with a serving of spaghetti containing 60 grams of starch, you'd only end up absorbing about 4 fewer grams of carbs and about 16 fewer calories.

Yet, some studies have found that carb blockers may cause moderate weight loss, especially when your carb intake is high. In one study, carb blockers caused the greatest weight loss in people who ate the most carbs (8, 9, 10, 11).

On the other hand, a 2011 review of studies concluded that larger, high-quality studies on carb blockers are needed to determine whether they are effective for weight loss (12).

In addition, carb-blocking supplements may cause digestive issues in some people, such as gas, diarrhea and bloating.

Overall, you shouldn't reply on carb blockers to produce significant weight loss.

Summary: Carb blockers or starch blockers inhibit the enzyme responsible for starch digestion. However, they can't block complex carb absorption altogether and their effect on weight appears minimal.

3. Juicing, Cleanses and Detoxes

Various cleanses and detox diets have become very popular lately.

In addition to promising fast weight loss, they typically claim to purge your body of "toxins" that build up over time.

Here is a list of several methods of detoxing or cleansing, which can last anywhere from 1–21 days:

  • Drink nothing but water for up to seven days
  • Consume only fresh fruit and vegetable juices
  • Drink specific liquid mixtures, such as lemonade sweetened with maple syrup and cayenne pepper
  • Consume only clear liquids while taking laxatives, enemas or herbs to "colon cleanse"

Because they are so low in calories, these diets can produce quick weight loss. For instance, some detox plans claim you can lose up to 21 pounds in 21 days.

However, the majority of the weight lost on these cleanses is likely water, especially during the first few days when weight loss is most rapid.

With the exception of one small study in overweight Korean women, no studies have looked into these claims or people's ability to maintain the weight they lose during a cleanse or detox (13, 14).

In the Korean study, women drank a lemon-syrup mixture containing fewer than 500 calories for seven days. Although they lost weight and improved some heart health markers, they also lost an average of 0.6 pounds (0.3 kg) of muscle (14).

This muscle loss isn't surprising, given that cleanses usually provide fewer than 20 grams of protein per day. To protect muscle health, adults need at least 0.45 grams of protein per pound (1 gram per kilogram) or a minimum of 50 grams daily (15).

What's more, your protein needs increase during weight loss. Higher protein intake has been shown to help prevent muscle loss in people who are actively losing weight. Also, the more muscle you have, the more calories you burn at rest (16, 17, 18).

Additionally, animal research suggests that low-protein diets increase the production of NPY, a hormone that drives hunger and belly fat storage (19, 20).

Finally, as far as ridding your body of toxins, your liver and other organs already perform this function every day. "Detoxing" your body is completely unnecessary.

In fact, it's best to steer clear of these detoxes and cleanses altogether.

Summary: Juicing, detoxes or cleanses may produce rapid weight loss, but a large portion of this weight loss is water. They also contain very little protein, which can lead to muscle loss and a slower metabolism.

4. Crash Diets and Fad Diets

Crash or fad diets have always been popular because they promise fast weight loss if you follow very specific guidelines.

Some of the most well-known crash diets have been around for decades and new ones are constantly being created.

Here are a few examples of popular crash or fad diets:

  • Cabbage Soup Diet: This diet promises weight loss of up to 10 pounds in 7 days. Each day you eat all you want of one or two types of food. You also consume a soup made from cabbage and other vegetables every day.
  • Grapefruit Diet: This classic crash weight loss plan was created in the 1930s and based on grapefruit's supposed fat-burning properties. In addition to grapefruit at every meal, you consume low-carb, high-protein foods like eggs and meat.
  • Five-Bite Diet: This approach involves eating anything you want, but it only allows you to take five bites per meal. It was created by Dr. Alwin Lewis, who promises weight loss of up to 15 pounds per week.
  • Baby Food Diet: On this diet, you replace 1–2 meals per day with several jars of baby food containing 25–75 calories each, consumed at one-hour intervals during the day.

Although some of these diets sound amusing, they aren't a good idea if your goal is sustainable weight loss. They aren't well balanced, nutritious or based on science.

Most of them are very low in calories, which can certainly produce quick weight loss in the short term.

However, research has shown that severe calorie restriction can lead to a reduction in metabolic rate, loss of muscle mass and rebound hunger that makes weight regain inevitable (21, 22).

In addition, these fad diets are typically low in protein. As discussed previously, this can cause many of the same effects as drastic calorie restriction.

One study from 1996 even suggests that very low-calorie diets may lead to insulin resistance and diabetes in some individuals (23).

In the case of the Grapefruit Diet, which does provide adequate protein and calories, there is no evidence that grapefruit increases fat burning. Thus, any weight loss experienced on this plan will mainly be due to its high protein and low carb content.

Summary: Crash or fad diets rely on gimmicks and promises of rapid weight loss. However, they are typically unbalanced, low in calories and protein and associated with weight regain.

5. "Fat-Burner" Pills

Taking a pill that helps you burn fat may seem like the perfect solution for taking weight off quickly.

However, some of these pills contain questionable ingredients that may end up doing far more harm than good.

Caffeine is one of the main ingredients in many "fat-burner" products. It has been shown to help you burn more calories when consumed in either beverage or pill form (24, 25, 26, 27).

In one study, men experienced a boost in metabolic rate after consuming a supplement containing caffeine and antioxidants like EGCG, which is found in green tea (27).

Although modest amounts of caffeine are safe and may help promote fat loss and boost physical performance, some fat burners contain substances that may cause dangerous side effects.

Reports of liver damage and other health problems have been linked to certain fat-burner supplements, including those that contain DNP and usnic acid (28, 29, 30, 31).

In two cases, previously healthy young women developed liver failure that required a liver transplant after taking fat burners containing usnic acid (30, 31).

Ironically, ads for fat-burners and weight loss pills are often found in women's fitness magazines that promote a healthy lifestyle (32).

Instead of taking pills that contain potentially harmful ingredients, drink a few cups of coffee or green tea daily.

Summary: Fat-burner pills contain caffeine and other ingredients that may boost metabolism. However, there is no evidence that these pills are more effective than caffeine alone and some have been linked to liver damage.

6. Eating Only One Food

Eating only one food has been a popular quick weight loss approach for decades.

Known as monotrophic eating or "mono eating," it involves eating as much as you want of one food for several days. Examples include eating only fruits, eggs, potatoes or cookies.

Like the other methods discussed, rapid short-term weight loss can occur with this strategy. This is mainly due to becoming so tired of eating only one food that your calorie intake automatically decreases.

One problem with this eating strategy is that it's unbalanced. While eating only eggs provides far more protein and other nutrients than a diet consisting of potatoes or cookies, it lacks the fiber and antioxidants found in plant foods.

There are few, if any, studies on mono eating. However, anecdotal evidence suggests that people almost always regain the weight after the diet is over.

And like other diets that severely restrict food choices, it doesn't help you develop eating habits that will lead to successful weight maintenance.

Summary: Eating only one food may cause weight loss due to an automatic reduction in calories. However, this unbalanced approach can't be maintained long term and often leads to weight regain after the diet is over.

7. Raspberry Ketones

Raspberry ketones are compounds found in red raspberries and other berries and fruits.

They are frequently used to add flavor and fragrance to foods and cosmetics. In recent years, they have also been marketed as a weight loss supplement.

It's claimed that raspberry ketones boost fat burning and increase levels of adiponectin, a hormone that has anti-inflammatory effects and helps regulate metabolism (33).

Although adiponectin is produced by fat cells, obese people generally have much lower levels of adiponectin than lean people.

Early studies in mice and rats found that raspberry ketones increased fat burning and helped protect against fatty liver. However, the dosages these animals received were extremely high (34, 35).

But very little research has been conducted in humans and so far the results aren't that impressive.

One supplement that contained a combination of ingredients, including raspberry ketones, was found to increase fat loss in obese people, but only when combined with diet and exercise (36).

On the other hand, a 2016 study found no significant difference in metabolic rate or fat burning among people who took raspberry ketones, compared to those who received a placebo pill (37).

At this point, research doesn't support the use of raspberry ketones for weight loss.

Summary: Although raspberry ketones have been found to increase fat burning in mice at very high dosages, the few human studies available have shown little to no benefit for fat loss.

The Bottom Line

Many diet plans and products promise quick weight loss.

But while some may take off weight temporarily, they're unlikely to help you achieve your goal of losing body fat and keeping it off.

In addition, these "quick-fix" approaches may lead to health problems, disordered eating and regaining more weight than you lost.

The only solution for sustainable fat loss is to follow a well-balanced diet that works for you and stick to it in the long term.

Reposted with permission from our media associate Authority Nutrition.

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