Do Diets Work for Quick Weight Loss Explained

Nowadays, there are many modern diets that promise fast and healthy weight loss.

While they are quickly gaining popularity, actual medical evidence for their positive effects and long term-application for weight management is mixed or insufficient.

Some of these diets might not be suitable for some, or even dangerous for others.

In this article, we will go over the effectiveness of popular diets for quick weight loss and health improvement.

The ketogenic diet can be healthy but still hides risks

The ketogenic diet is a quite popular diet for quick weight loss and other health benefits.

It is an extremely low-carbohydrate, high-fat and average in protein type of diet.

It is based on the metabolic state of ketosis which turns fat into ketones for fuel instead of glucose when there are no carbohydrates in the diet.

In order to achieve that, you have to consume less than 5% of your daily calories from carbohydrates (roughly 20-30g) and more than 75% of fat.

For protein, the amount should be no higher than 20% because protein can also be transformed into glucose by the body.

This means that the diet excludes foods like sugar, grains, fruits, legumes, starchy vegetables, roots, alcohols (even as sweeteners), sauces, etc.

Seeds and nuts also contain some carbohydrates and can easily get you above the threshold of 20g per day, so they should be avoided as well.

Foods to eat, in order to maintain the diet, include lean meat and meat products, fish (especially fatty fish), eggs, some types of cheese, healthy oils (olive, flaxseed), avocados and low-carb veggies (green, leafy, onions, pepper, tomatoes, etc.).

Although the diet also allows the consumption of red meat, processed meat, butter, mayo, coconut oil, etc., these products have high amounts of saturated fat and some are even carcinogenic, so they should be used sparingly.

The diet is very successful as a weight-loss method – a review of multiple studies shows that the rate of fat loss is comparable to any other effective and healthy diet (1).

Another massive meta-analysis showed that in the short term, the ketogenic diet might lead to faster results, however in the long term weight loss is again comparable (2).

Subjects lost 1 kg more on average during the 1^st year, but the low-fat diet caught up with the rate of weight loss during the 2^nd one.

A theory was proposed, that because of the lack of carbohydrates and thus insulin, fats cannot be stored in the fat cells and this results in this dramatic weight-loss.

However, that theory was proven incorrect (3). Even without insulin, when there is an excess of calories, fat can be stored via a hormone called acylation stimulating protein.

The actual reason that the diet is effective in terms of weight loss is that by avoiding carbohydrates entirely, we simply restrict our dietary choices so much, it usually results in significant caloric restriction.

This is the principle for any other weight loss diet as well – without enough energy intake, our body has no choice but to lose weight.

The diet is also helpful because ketones are proven by studies to have hunger suppressing effects (4).

The initial quick loss of weight is also likely a result of water loss, and in the long term, the rate is rather average.

From a health standpoint, the diet can be helpful for the management of epilepsy.

Ketones are proven to have seizure suppressing effects on the brain, comparable to those of the standard medication therapy (5).

The diet has also been speculated to be helpful in the treatment of cancer and diabetes.

However, it has some disadvantages in terms of health. It is a quite restrictive diet, which demands you to avoid many healthy foods like fruits, starchy vegetables, legumes, and nuts.

Reducing the total number of dietary choices so much makes it harder to adhere to.

Also, the diet has a number of side-effects, first of which is the keto-flu.

It is caused by the transition of the organism from burning carbohydrates into burning fats and producing ketones.

The symptoms last about a week and vary from person to person.

They usually include nausea, vomiting, stomach pain, headache, poor sleep and concentration, and cravings.

These symptoms can be relieved by staying hydrated, taking electrolytes like magnesium and avoiding exercise.

The ketogenic diet has other unpleasant side-effects such as breath smelling like acetone.

Acetone is actually one of the ketones that now your liver produces. It is an extremely common side-effect and can be managed by regularly chewing sugar-free gum.

A lot of people also suffer from constipation when following the diet.

For people who find it hard to adapt to it, the diet might cause episodes of hypoglycemia which is a dangerous condition.

There is also a lack of evidence about the long term health effects of the diet.

The diet generally does not restrict the amount or the type of fats consumed.

While initially, the diet had positive effects on cholesterol levels because of the fat loss, consuming too much saturated or hydrogenated fat might increase cardiovascular risk in the long run.

Take-Away:

The ketogenic diet can lead to quick weight loss and health benefits, however, not everyone tolerates ketosis well.

Atkin’s diet – easier to follow, but with caution

This is another low-carbohydrate diet, however less restrictive in comparison to the ketogenic diet.

Since it is not entirely based around ketosis, the diet allows the slightly higher intake of protein – around 30% of your daily energy intake and carbohydrates up to around 100g per day.

In order to initiate quick weight loss, the diet suggests phases.

The 1^st phase is called induction and it is the same as the ketogenic diet – complete restriction of carbohydrates to around 20-30g per day for the first 2-3 weeks.

High-fat, high-protein meals are allowed, like meat, fatty fish, oils, some types of cheese and only low-carb green and leafy vegetables.

This leads to fast results, which are partially due to water loss as well.

If the side-effects of the keto-flu are too severe, the diet suggests skipping the 1^st phase and beginning from the 2^nd one.

During phase two, called on-going weight loss, you start with the low carbohydrate intake from phase one, but progressively increase it by 5-10g per week, until you reach 40-50g of carbohydrates per day.

This allows you to consume more fresh fruits, starchy vegetables, nuts, seeds, and legumes.

However, foods higher in carbohydrates like sugary foods, juices, snacks, sweets, grains should still be avoided entirely.

For the 3^rd phase, called fine-tuning, you increase your carb further every week until you reach 100g per day and still keep avoiding high-carbohydrate foods.

Eventually, the 4^th stage which is the maintenance will require you to keep controlling your carbohydrates and reduce your intake to earlier stages if you start gaining weight again.

Compared to other diets, the Atkins diet also results in significant weight loss (6).

The effect is again not due to the low-carbohydrate content per se, but because of the resulting calorie restriction from limited food choices, increased excretion of water, suppression of appetite from ketones, and increased satiation from the higher protein content (7).

From a health standpoint, the Atkins diet allows a higher variety of food choices which makes it easier to follow.

It has similar effects to patients with epilepsy in terms of seizure control while allowing for better adherence.

Even though complete ketosis here is mostly avoided, the diet might lead to the side effects and concerns associated with it.

There have been cases of induced ketoacidosis in subjects following the diet (8).

Consuming lots of saturated fats and hydrogenated oils might again hide increased cardiovascular and other health risks in the long term.

Take-Away: This is an easier diet to follow compared to the ketogenic diet while having the same benefits, but still it is not suitable for everyone

The Dukan diet – a very high protein approach

This diet involves a restriction of both carbohydrates and fats.

It is a high-protein diet without any restriction on the total amounts consumed.

The diet is indeed effective for a quick weight loss, because of the dietary restriction resulting in reduced energy intake.

Also, high protein consumption improves satiation and thermogenesis (9).

Protein has higher-energy costs to be digested and transformed into glucose through the process of gluconeogenesis (10).

The allowed foods are lean meats, poultry without the skin, low-fat dairy, eggs, non-starchy vegetables, oat bran, and meat substitutes.

Forbidden are nuts, avocadoes, fatty meats, legumes, starchy vegetables, fruits, full-fat dairy.

While the diet results in quick weight loss, one of the few studies investigating the Dukan diet found significant negative effects on overall nutritional status (11).

51 women had a significant weight loss in a short period, however, they developed deficiencies of vitamins and minerals.

The diet also hides risks for kidney health.

High protein intake could be an unhealthy habit in people with kidney disease, even in the early stages when kidney function is only slightly reduced (12).

In healthy kidneys, however, no damage was observed by multiple studies, even in trials with protein levels up to 2.8g per kg of body weight (13, 14).

The Dukan diet restricts a lot of healthy food options like nuts, fruits, legumes, and starchy vegetables which might increase the risk of deficiencies.

Despite including oat bran as an obligatory meal every day, the low amounts of total fiber in the diet might increase the risk of cardiovascular diseases.

There also have been cases of ketoacidosis with the Dukan diet (15).

Take-Away: The Dukan diet can result in very quick weight loss, however it restricts too many healthy options from including both fat and carbohydrate sources.

Paleo diet – based on the diet of our ancestors?

This diet is based on the belief that the diet of our ancestors who were hunters and gatherers is optimal for human health.

It is presumed they did not suffer from obesity or diabetes. This involves the period specifically before agriculture was developed.

It is actually impossible to know what the diet of our ancestors looked like and these are only speculations.

We should not overlook the fact that apart from their diet, they had a very high physical activity that played a significant role in terms of weight management and metabolism.

However, there is scientific evidence that following a paleo diet does lead to weight loss and brings some health benefits as well (16).

A study showed improvements in body weight, waist circumferences, and blood pressure.

Further evidence suggests the improvement of cholesterol and blood sugar levels following weight loss with a paleo diet (17).

The weight loss effect of this diet is again based on restrictions.

All foods that are considered processed have to be avoided, including grains, legumes, dairy, sugar, sugary foods or beverages, hydrogenated oils, artificial sweeteners, and any highly processed foods containing food replacements.

The allowed foods are lean meat, fish, eggs, vegetables, fruits, nuts, seeds, herbs, and healthy virgin oils(olive, flaxseed).

While the diet restricts a lot of unhealthy foods like hydrogenated oils, it also restricts healthy and nutritious dietary options like dairy, grains, and legumes.

Furthermore, the diet restricts the use of salt, sugar or other additives.

Problems with the diet are related to those restrictions that lead to reduced adherence and palatability.

A lot of the pleasure caused by the food is lost, which makes it harder to follow.

Also, the lack of any dairy products can lead to deficiencies, such as calcium deficiency. Increased incidence of it is proven with scientific evidence (18).

Take-Away:

The paleo diet leads to weight loss and health improvements but at the cost of increasing the risk for some deficiencies as well as reducing the pleasure and taste of the food.

Vegan diet – not healthy without heavy supplementation

This is a diet that aims to exclude all animal products from a person’s nutritional habits.

The reasons for that are not only related to health but also ethical and environmental.

While vegetarians avoid mostly meat, vegans avoid also dairy, eggs, fish, and animal-derived products – honey, gelatin or supplements.

Because of those restrictions, the diet is usually low in fat and high in fiber.

The low fat content contributes to lower overall energy intake, thus a caloric deficit that results in weight loss.

The high fiber aspect increases satiation and adherence to the diet, as it helps manage hunger better.

These aspects are supported by scientific evidence, as a review of multiple studies shows significant benefits of following a plant-based diet in terms of weight-loss (19).

Still, this does not make a vegan diet more effective for weight loss compared to other calorie-restricted diets.

While avoiding red meat and processed meat can indeed reduce the risk of cardiovascular diseases, cancer, and overall all-cause mortality (20, 21, 22, 23), restricting all forms of animal products is not necessary for optimal health.

Quite on the contrary, veganism is proven to increase the risk of multiple deficiencies, including vitamins, minerals, and essential nutrients.

The most common deficiency amongst vegans is iron deficiency (24).

Although iron is also found in plant food sources, we cannot digest and absorb the form of the iron in the plants properly.

This is why we need to consume a combination of plant and animal food sources.

Vegans are commonly deficient in vitamin D and B12 because the best sources for those vitamins are also animal products (25, 26).

Another problem with veganism is getting enough omega 3 fatty acids (27).

Compared to those contained in fish, omega 3 coming from plant sources acts only as a precursor for their synthesis.

Much higher amounts from plant sources are required to reach normal levels in the blood, thus it is much more efficient to consume fish or fish oil supplements.

Take-Away: While it can be a good diet for weight-loss, veganism requires heavy supplementation with iron, vitamin B12, vitamin D, and Omega 3 fatty acids.

The zone diet – lots of claims, very little evidence

Another diet involving following a strict ratio of proteins, fats, and carbohydrates.

The ratio is very specific: 30% protein, 40% carbohydrates and 30% fats.

The diet largely revolves around consuming carbohydrates with a very low glycemic index.

It is a value that compares how different foods impact blood sugar levels in comparison to pure glucose, which is accepted as a value of 100.

The glycemic index of most foods was derived from the testing of healthy subjects. Science has collected data for 2500 different food items (28).

Bigger the value, higher the raise in blood glucose. Generally, a glycemic index below 55 is considered low, while above 70 is high.

Good sources of low-glycemic index foods are some fruits like citrus and barriers, non-starchy, green and leafy vegetables, whole grains.

Protein sources should be lean, including low-fat meats and poultry without the skin.

Fats should be exclusively mono or polyunsaturated, while saturated fat sources like animal fat, butter, palm, coconut oil, and others should be avoided.

Foods to be avoided include all sources of carbohydrates with a medium to a high glycemic index.

This includes dried fruits, fruits with a high glycemic index, starchy vegetables, bread and other white-flour products, sugar and sugar-containing foods and beverages, sweets, candy

In order to maintain the recommended ratio of nutrients, without counting calories, it is recommended to use the plate method.

The methods consist of controlling the size and the ratio of your portions. One-third of the plate should be lean protein, roughly with the size of your palm.

The other two-thirds should be of according size and consisting of vegetables or grains with a low glycemic index.

Very low amount of additional fat can be added (olive or flaxseed oil) because some fat is already contained in the source of protein.

The zone diet is proven to be effective in terms of weight loss and improvement of cholesterol and blood sugar levels (29).

The reason that this diet works in terms of weight loss, is because it promotes control over the size of the portions consumed.

It also has a higher ratio of protein, which provides satiation and has higher energy costs to be digested.

However, the additional claims made by the diet, that it reduces inflammation or that the proposed ratio of macronutrients is optimal are not confirmed by evidence (30).

Because of the requirement for a low glycemic index, the diet leads to the restriction of some healthy food choices like bananas, grapes, mangoes, peas, corn, carrot, potatoes, and cereals.

Glycemic index, however, has severe limitations – it is determined for 50 grams of carbohydrates for each food.

However, a normal portion of some of those foods with glycemic index above 55 contains much lower amount of carbohydrates and thus does not have a big impact on blood sugar levels.

This means avoiding the healthy foods mentioned will not bring any benefits.

Take-Away:

The diet is helpful in creating good dietary habits – control of portions and food sources. However, it makes some health claims that lack evidence and restricts healthy food options.

The bottom line on different diets for quick weight loss

Many diets have claimed that they are healthy and can result in quick fat-loss.

However, a lot of these diets involve restrictions, which do not follow the rules of healthy eating and potentially might have detrimental effects for some people.

They achieve their quick weight loss by severe restrictions in dietary options which in turn results in significant caloric deficit, to produce the effect.

At the same time, they claim that counting and restricting calories are not needed to lose weight.

It is important to remember two things – first of all being thin and skinny is not the same thing as being healthy.

Secondly, the best diet to achieve weight-loss is the one that suits your schedule, it is easier to adhere to and does not restrict healthy food options.