Millions of people try a new diet as part of their resolutions each new year.
Unfortunately, the vast majority of these diets fail before January is over.
The fact of the matter is that most people undertake diets that don’t fit with their lifestyle, grow tired of them, and give up.
In other words, not all diets are equally suitable for everyone, and the key is to find the right way of eating for each individual.
This article looks at the factors that make a diet successful, the pros and cons of popular diets, and how to find the eating plan for you.
What makes a diet successful?
It is easy to achieve short-term success on any diet, give up, and then see the weight rebound.
But how can we make the way we eat sustainable?
Firstly, we shouldn’t just follow the latest celebrity diet or a diet that friends are trying (it’s a myth that one diet is right for everyone).
Instead, the key to a successful way of eating is to find one that fits our lifestyle.
Here are three elements that any successful diet should consider.
1) The diet should be enjoyable and consider the individual
First of all, one of the most important “rules” for any diet should be that we enjoy the food we are eating.
If we do not enjoy the way we eat, then the idea of sticking to the diet becomes a chore, and it ultimately becomes unsustainable.
This is one of the primary reasons why most diets fail.
For those who love potatoes and fresh fruit, a strict ketogenic diet that eliminates them may not be the ideal choice.
In like manner, a strict low-fat diet is a poor idea for people who love steak, cheese, and chocolate.
If we enjoy the way we eat, then it is much more likely that we will be able to sustain the diet over the longer term.
To enjoy our food, we need to pick a way of eating that caters to our likes and dislikes.
2) The diet should be nutrient-dense
Enjoying the food we eat is important, but when we follow a diet over the longer-term, it is also crucial that we are eating in a health-supportive manner.
While there are lots of different factors that determine whether or not a diet is healthy, half of the battle is focusing on nutritious whole foods.
By focusing on whole foods, we ensure that each meal we are eating offers:
- A good range of essential nutrients.
- A lack of ultra-processed, energy-dense ingredients such as sugar, refined flour, and added fats/oils.
While it isn’t necessary to eat in this way 100% of the time, if we strive to base our meals on whole foods, we can at least guarantee a beneficial range of nutrients.
For some healthy ideas, here are some of the most nutrient-dense foods from both animal-based and plant-based foods.
3) The diet should be satiating
Regarding the energy value of a specific food, one calorie will always be one calorie.
However, not all calories have the same effect, and the nutritional composition of food is a crucial consideration.
The food we eat can also have very different effects on our subjective levels of satiety. If the food we eat is filling, then this can help to discourage food cravings and subsequent poor nutritional choices.
Additionally, sources of carbohydrates that contain fiber and provide a larger volume of food also increase satiety. This is one reason why food choices such as potatoes and oats suppress appetite compared to refined carbohydrates (3, 4).
In short, consuming a source of protein at each meal and opting for fibrous sources of carbohydrate rather than refined carbs may help with appetite regulation and controlling food intake.
Pros and cons of popular diets
Providing we eat the right foods in the right amounts, it is not necessary to follow a specific dietary system.
However, for those who are interested in different ways of eating, here is a look at some of the positives and negatives of common diets.
1) Ketogenic diet
The ketogenic diet, known as “keto” for short, has been trendy over the past few years.
The diet tends to involve:
- Restricting dietary carbohydrate intake to about 5-10% of total calories (5).
- A primary focus on dietary fat followed by protein.
- Higher amounts of animal foods such as dairy, eggs, fish, and meat.
- Low-glycemic, non-starchy fruit and vegetables such as asparagus, bell peppers, and mushrooms.
The ketogenic diet may be suitable for those who prefer a higher fat intake and don’t particularly want to consume grains, potatoes, or other high-carb foods.
However, like most diets, adherence (sustaining the diet) can be an issue. For example, a systematic review and meta-analysis of twelve studies found that the average adherence rate to a ketogenic diet was 45%. Further research found that approximately 45-50% of participants undertaking a ketogenic diet didn’t complete the study (8, 9, 10).
Depending on the specific food choices, a ketogenic diet can be very nutrient-dense. For instance, the menu might include nutritious whole foods such as berries, meat, nuts, seafood, seeds, and vegetables.
On the other hand, it is possible for dieters to over-consume fat at the expense of more nutritious food choices.
In recent years, a more extreme version of the ketogenic diet has become popular called the carnivore diet. This way of eating focuses only on animal foods and restricts plant foods.
In other words, this means a diet of meat, dairy, seafood, eggs, and that’s about it.
Perhaps surprisingly to some, such a diet can provide a good range of nutrients, and focusing on nutrient-dense foods like organ meats and shellfish can help with this.
However, some forms of the diet tend to be just about eating meat and water, and nothing else. This form of the diet can make it challenging to consume the recommended levels of several nutrients, such as vitamin C.
Additionally, the diet does not provide some non-essential (but likely optimal) nutrients like fiber and polyphenols.
2) Low-carb diets
General low-carb diets are very similar to the ketogenic diet, but they are more lenient with the upper carbohydrate limit.
For example, some researchers class diets with up to 150 grams of carbohydrate per day as “low carb” (11).
Low-carb diets either have a more significant focus on dietary fat, like the ketogenic diet, or they can focus on higher protein intake, similar to Atkins-style diets.
Generally speaking, low-carb diets involve:
- A greater focus on animal-based foods such as meat and seafood.
- A carbohydrate intake ranging from very low amounts to upper limits of 100-150 grams per day.
- Low to moderate intake of higher carbohydrate fruit and vegetables such as apples, bananas, and potatoes. Despite this, low-carb diets support the liberal consumption of berries and non-starchy vegetables.
Low-carb diets offer similar benefits and drawbacks as ketogenic diets, but they are are not as strict regarding carb-restriction.
For this reason, they may be a better choice for those who enjoy eating more fruit and vegetables.
3) Low-fat diets
Low-fat dietary plans emphasize large amounts of carbohydrates and limit dietary fat intake.
Research shows that low-fat diets are also a useful tool for weight loss. In a systematic review and meta-analysis of 33 randomized controlled trials, the average weight loss after at least six months was 1.6 kg (12).
Once again, adherence is a crucial issue to consider. On this note, a recent clinical trial featuring 148 adults found that the participants had similar adherence to low-carb and low-fat diets (16).
Popular diet plans such as DASH are a form of the low-fat diet, and these diets typically involve:
- Higher intake of grains, legumes, and starchy carbohydrates.
- Large amounts of fruits and vegetables.
- Restricted dietary fat consumption.
- Lean meat and low-fat dairy, and a lower intake of fatty animal foods.
Low-fat diets may be best suited for people who enjoy higher-carbohydrate foods such as grains, legumes, tubers, and fruit.
However, it is worth noting that dietary fat intake shouldn’t be overly restricted.
For instance, fat is important for the optimal absorption of fat-soluble vitamins, and certain fatty acids—such as omega-3 and omega-6—are essential. These are some of the reasons why the World Health Organization urges a minimum fat intake equivalent to 20% of total calories (17, 18).
4) Mediterranean diet
In truth, there is no single “Mediterranean diet,” and the dietary patterns and food choices in the region can vary from place to place.
However, the generic definition of a Mediterranean diet tends to focus on seafood, fruit, vegetables, cereals, legumes, nuts, dairy, and olive oil (19).
Based on three different Mediterranean diet pyramids, the above foods are recommended on a daily to frequent basis. These pyramids also include a less frequent, ‘low to moderate’ recommendation for red meat, poultry, sweets, and red wine (20).
Once again, this dietary system may have benefits because it encourages higher intake of whole foods and lower levels of ultra-processed food.
According to systematic reviews and controlled trials, people living in the Mediterranean region (and consuming a Mediterranean diet) also tend to display lower rates of obesity, cardiovascular disease, and cancer (21, 22, 23).
However, it is difficult to ascribe these benefits solely to their diet.
Mediterranean diet templates are not as restrictive as other diet plans and may be suitable for those who enjoy a little bit of everything.
5) Vegetarian diet
Vegetarian diets restrict meat and fish, largely due to an individual’s ethical beliefs about animal slaughter.
However, these diets do include other animal-based foods such as dairy and eggs. For this reason, it is easier to prevent nutritional deficiencies on a vegetarian diet compared to a strict vegan diet.
- Omega-3 fatty acids
- Vitamin B12
- Vitamin D
For this reason, it is essential to plan the diet carefully to meet these nutritional requirements.
Providing the diet is nutritionally adequate, vegetarian diets may be a good choice for those who wish to avoid meat and fish.
6) Vegan diets
Vegan diets have increased in popularity over recent years.
Generally speaking, people usually follow the diet as an ethical choice due to personal opinions on the use of animals for food.
However, the diet can be quite restrictive as it allows no dairy, eggs, meat, seafood, or anything made with these foods.
Aside from animal welfare considerations, some people may follow the diet due to the purported health benefits of plant-based dietary patterns.
However, less is known about the effect of strict vegan diets on cognitive health, and the current evidence in this area is inconclusive (30).
It is also possible that many vegan dieters are more health-conscious than meat-eaters, which may explain some of the positive studies on plant-based eating.
For instance, a recent cross-sectional study that followed 146 participants found that their health biomarkers were more closely related to diet quality rather than plant-based food intake (31).
Potential nutrient deficiencies
A positive point about vegan diets is that they include lots of nutrient-dense foods that are relatively low in energy.
However, a potential issue with these diets is that there can be a significant risk of nutrient deficiencies, particularly for vitamin B12.
In the European Prospective Investigation into Cancer (EPIC) study, more than 30251 participants were followed, including 6673 vegetarians and 803 vegans. While vegans had an impressive intake of vitamins C and E, folate, magnesium, iron, and copper, there was a “high prevalence” of vitamin B12 and iodine inadequacy (32).
To be specific, the rate of vitamin B12 inadequacy stood at 84.8% for vegan men and 89.0% for vegan women. In contrast, these figures stood at just 0.1% for meat-eaters and 17% for vegetarians (32).
With adequate supplementation, though, vegan diets can be nutritionally complete.
Here are some of the nutrients of concern for vegan diets and how to get them.
What is the best diet for me?
To reiterate the first part of this article, the “best” diet should:
- Include foods that we enjoy.
- Prioritize nutritious, whole foods – food quality is important.
- Be satiating.
- Suit our lifestyle.
To put it another way: the best diet is the one that we can follow in a healthy and sustainable manner.
Beyond this, there is no real need to follow a specific dietary system.
That said, some people find following a diet and being part of a particular diet community—and the support system that provides—to be helpful. Following one of the typical diet plans highlighted here may help with this.
Lastly, counting calories and tracking what we eat isn’t always necessary, but it can be helpful for those who have difficulty knowing the right amount to eat.
For more nutrition articles, see these guides.