Top 5 Weight Loss Diets: Pros & Cons

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We lose weight when our body uses up its sugar stores and starts burning fat after hours without food. Alternatively, if more calories are depleted than consumed, it can also lead to weight loss.


When choosing a weight loss diet, we often place our focus on how much pounds we can shed or how prompt the results are… In fact, sustainability is the key to an effective, satiating weight loss diet. Afterall, not everyone can hold on to a diet plan for life, especially if it involves giving up some of our favorite foods entirely, or that it takes massive efforts to keep going. Even if you’re making headway with a restrictive diet, the result may hardly last in the long run.


Another big challenge is to choose “the one”. There is no shortage of diets available — the sheer number of meal plans on the internet is overwhelming enough. Don’t stress it! We have done the groundwork in comparing and cherry-picking the best diets for you, based on each of their working mechanisms, weight loss effect, other health benefits and potential drawbacks. Read on to learn more.

1. Intermittent fasting

No, intermittent fasting does not just gain ground recently. It is an eating pattern adapted throughout human evolution history, characterized by consecutive eating and fasting sessions. 


How does it work?

This diet is easy to follow with no restriction on what you eat, but only when you eat. There are numerous methods of intermittent fasting, namely:

  • Alternate Day Fasting
    • Fasting for 24 hours once or twice per week on non-consecutive days. 
    • E.g. Fasting on Monday and Thursday, eating for the rest of the week.
  • Modified Fasting
    • This method, also known as the 5:2, requires a reduced calorie intake, i.e. 20-25% of normal calorie intake (normally 500 calories for women and 600 calories for men) on 2 non-consecutive days, and normal calorie intake for the remaining 5 days of the week. 
    • E.g. A reduced calorie intake on Monday and Thursday, and normal eating for the rest of the week.
  • Time-restricted Fasting
    • There are different types of time-restricted fasting, i.e. 12/12, 14/10, 16/8, etc. The number before the slash is the number of consecutive fasting hours, and that after the slash is the number of eating hours. This method is practiced throughout the week. 
    • E.g. For the 16/8 method, eat during 12pm–8pm, and fast from 8pm until 12pm on the second day.


Weight loss effect

One of the main purposes of intermittent fasting is to cut back on calorie intake by fixing eating sessions within a certain time frame.


A review article by the University of Illinois at Chicago revealed that a 2–12 week intermittent fasting regime can bring about a 3-8% reduction in body weight, which is more significant than traditional calorie restriction methods.


The same article also showed comparable reductions in visceral fat mass (fat around the abdominal area, also a risk factor of cardiovascular diseases) through both intermittent fasting and the traditional methods, implying that intermittent fasting might be an effective weight-loss method even without the need to restrict calorie intake.


Other health benefits

Intermittent fasting has been associated with enhanced gut health and immunity, disease prevention, longevity, cognitive health and metabolism.


It is a relatively easy and sustainable regime to practice indefinitely as a lifestyle change — and should get easier when you grow used to a fixed routine (e.g. start eating at 12pm and stop eating at 8pm). 


Potential drawbacks

For people who have special medical conditions e.g. diabetes, cancer, lower blood pressure, cardiovascular disease, eating disorder, underweight, as well as for pregnant/breastfeeding women, it is recommended to consult a doctor or dietitian beforehand to assess whether this diet is suitable for your body condition.

2. Vegan/vegetarian diet

Vegan or vegetarian diet is a plant-based diet which shifts from heavy reliance on meat and animal products to whole foods such as whole grains, fruits, vegetables, beans, peas, nuts and seeds. It provides more fiber, antioxidants, vitamins and minerals for your body’s needs.


How does it work?

While vegetarian diets abstain from meat intake and primarily rely on plant-based foods,  vegan diets take a step further and exclude all or most meat, offal and animal products — including eggs and dairy products. There are 4 varieties of vegetarian diets:

  • Ovo-vegetarian diet
    • Excludes all animal products and dairy products, with the exception of eggs. Eggs, duck eggs and quail eggs have similar calories, where quail eggs also have higher protein.
  • Lacto-vegetarian diet
    • Excludes all animal products and eggs, with the exception of dairy products. Dairy products, particularly cheese, are rich in protein. Low-fat or skimmed milk are helpful to better control your fat intake. High-calcium and low-sugar milk powder are also great dairy options.
  • Lacto-ovo-vegetarian diet
    • Excludes all animal products with the exception of eggs and dairy products. Egg-milk vegetarians are less likely to suffer from insufficient protein intake because both eggs and dairy products provide almost all of the essential amino acids (building blocks of protein) for the human body.
  • Vegan
    • The strictest type of vegetarian diet. All animal products, including eggs, dairy products, meat and offal, should be prohibited, same even for foods of animal origin, like bird’s nest and honey.


Weight loss effect

A 2019 biochemical research shows that a plant-based diet is effective for weight loss. The underlying mechanism is that the high fiber content of plant-based foods helps in appetite control and food intake reduction. Fiber in vegetables and fruits turn into a gel-like structure and expand in size after mixing with water or other liquids. The fibrous gel mass slows down the digestion and absorption process and stays in the stomach for a longer time. This sustains fullness and enhances a sense of satiety, thus reducing the urge to eat.


Other health benefits

A vegan or vegetarian diet can bring about improvements in insulin sensitivity, gut microbiota symbiosis, as well as the reduction in risk of chronic conditions, such as heart disease, diabetes and certain cancers. 


Potential drawbacks

A plant-based diet is generally healthy, but if managed improperly, vegans/vegetarians may be deficient in important nutrients only found in animal-based foods, e.g. protein, omega-3, vitamin B12, D, iron, calcium, iodine, zinc. Nutrient supplementation or careful diet planning are needed to prevent deficiencies.

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3. Keto diet

The ketogenic (keto) diet is a type of a low-carb, high fat diet typically adopted by people who want to lose weight over a relatively short period of time. The term “keto” comes from ketones (also known as ketone bodies) which the body produces when it burns fat for energy instead of sugars (i.e. glucose and starches from carbohydrates). By reducing carbs, our body enters into a metabolic state called ketosis.


How does it work?

To implement the keto diet, it is important to maintain a high-fat, moderate-protein and very low-carb ratio. You need to reduce your daily carbohydrate consumption: a common figure is no more than 20g of carbohydrates per day. Meanwhile, try to opt for healthy sources of fats whenever possible.


Weight loss effect

Keto diet has increasingly been used for weight management in recent years, with its fat loss effect.


Once your body is in a ketogenic phase, other than fat-loss, you can also benefit from a state of prolonged energy. Having a high-fat diet will likely keep you fuller for longer, and the process of energy breakdown will become more steady without the disruption of energy spikes, meaning better efficiency in your daily routines.


Other health benefits

The keto diet was originally created to treat patients with epilepsy, as an alternative to fasting and it had been proven to produce positive results. Studies showed that when patients went on a high-fat, low-carb diet, the regularity of their seizures was noticeably reduced.


The diet is also available to those with type 2 diabetes. As it is common for people with type 2 diabetes to be overweight with a pressing need for weight management, the keto diet comes in handy due to its heavy reliance on breaking down fat for energy, hence cutting down reliance on the production of insulin to manage blood sugar levels


Potential drawbacks

A word of caution: The keto diet may seem to cater to everyone’s needs, but in the case of any health conditions, it is best to get advice from a medical professional.


A common sign at the start of the keto diet is the “keto flu”: a set of symptoms some experience when switching to the high-fat, low-carb diet. You may also experience withdrawal-like symptoms as the body and the brain are still adapting to the sudden change of energy supply. It is important to stay hydrated throughout this process and rest if you feel sluggish and tired.


Once your body adapts to being in ketosis, these symptoms will fade away.

4. Paleo diet

The Paleo diet emphasizes getting rid of foods that have been processed using methods characteristic of modern human society. Instead, it promotes eating whole foods that are naturally grown and sourced — what would have been available to hunter-gatherers.


How does it work?

Following a paleo diet involves eating lean meats, fish, fruits, vegetables, nuts and seeds. Any food that appeared as a result of the advancement of farming are excluded. This means grains like rice, wheat (flour) and dairy products such as cheese, milk and yogurt are also eliminated.


To follow a lifestyle that resembles a caveman’s, you are encouraged to drink plenty of water and stay active, just as our ancestors would have back then.


Weight loss effect

As the paleo diet rules out processed foods and grains which are common sources of simple carbohydrates, the surging intake of vegetables and protein will use up more energy to break down, which will eventually lead to weight loss.


A randomized trial conducted in 2014 showed that the paleo diet significantly lessens the total fat mass, waist circumference and triglyceride levels in obese postmenopausal women.


Another study by a group of nutritionists in Australia, 2016, concluded that the paleo diet is more effective in achieving weight loss than a low-fat diet. It can also bring about positive changes in metabolic and cardiovascular risk factors.


Other health benefits

The paleo diet can increase insulin sensitivity, improve heart health, boost energy and reduce inflammation.


This diet centers on eating a wider range of nutrients and whole-foods, which means better nutrition for the body and the optimization of overall bodily functions as well as improvements in the removal processes of bodily waste. 


Potential drawbacks

  • Feeling down or unenergized

Due to the deduction of carbohydrates, you are likely to lose out on the mood-boosting effects offered by a carb-heavy diet. It may take some time to get used to the body state, but staying hydrated and trying to exercise more can help a tone in making the transition easier.

  • Craving sugary foods

Since the body is used to glucose as a main source of energy, such a sudden shift may cause strong cravings for a while until the body has a chance to adjust.

  • Working out may be tougher

As it will take some time to accommodate the body to different new energy sources, workouts may be temporarily even harder to get through. 


However, once the body adapts to this new diet, you may notice that workouts bring better results than before. This is due to improved nutrition as well as a higher intake of protein from eating more meat instead of grains.

5. Mediterranean diet

The Mediterranean diet was a traditional diet followed by many people living around the Mediterranean Sea back in the 1960s. These people, including French, Greek, Italian and Spanish, were found to have longer life expectancies and better health status.


How does it work?

The Mediterranean diet is largely a plant-based diet, with minimally-processed food of high fiber from whole grains, vegetables and fruits; unsaturated fats from fatty fish and seafood; quality protein and different micronutrients and a relatively low intake of animal-based foods.


The proposed rationale of weight loss is that the higher intake of healthy fat and fiber in a Mediterranean diet provide satiety and sustain fullness longer, reducing the urge to eat and thus overall caloric intake. 


Weight loss effect


The Mediterranean diet is not primarily a weight-loss diet. Nonetheless, as compared to a calorie-restricted low-fat diet, a calorie-restricted Mediterranean diet may be more effective for weight loss, based on a study by The Journal of the American Medical Association.


Other health benefits

The Mediterranean diet is associated with reduced risk factors for cardiovascular diseases and other chronic diseases such as high blood pressure and elevated cholesterol level, as numerous studies suggested. Recent research in Italy even explored how a Mediterranean diet may potentially slow down the process of aging.


The Mediterranean diet also helps prevent the onset of various mental health conditions, including depression, anxiety and other mood disorders.


Potential drawbacks

The Mediterranean diet requires the consumption of fatty fish at least twice a week. Nonetheless, certain fatty fish contain high levels of mercury, a heavy metal that damages the function of different internal organs. So, try to avoid king mackerel, orange roughy, marlin, shark, swordfish, tile fish and big eye tuna. Instead, go for salmon, haddock, canned light tuna and shrimp as the optimum sources of omega-3.


What is the best weight loss diet?

The sad news is that there is no such thing as the “best” weight loss diet. A certain weight loss diet may work wonders for some people, but have no visible result for others. 


It is important to choose an effective weight loss diet based on your personal eating pattern, dietary preference, body composition and the ultimate weight loss goal. If you have questions about which weight loss diet suits you better, consult a doctor or a dietitian for professional advice.

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This article was independently written by Healthy Matters and is not sponsored. It is informative only and not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be relied upon for specific medical advice.

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