The days of a weight loss plan simply involving calorie counting are long gone. The modern diet manipulates macronutrient consumption; it uses science (not always very accurately) to theorise over the best way to lose weight and it exerts its value by getting celebrity endorsements. Diets today aim to improve overall health, promising benefits that go way beyond reducing your dress size.
So, what do these diets involve? Is the science sound, or is attempting to adhere to them going to do you more harm than good?
In this article, we take five of the latest fad diets and review them; we look at their strengths and weaknesses, and we break down what they really do.
In recent years the Keto diet has garnered significant interest as a weight loss tool. A favourite of tabloid celebrities, 'keto' has become the latest buzzword in fitness and wellbeing networks. It's origins, however, are somewhat removed from this, with the ketogenic diet initially proposed as a means of managing treatment-resistant epilepsy. Considered to occur primarily as a result of metabolic dysfunction, sporadic seizures are not easy to manage. However, it has been shown that adopting a low-carbohydrate, high-fat, ketosis-inducing diet, stabilises brain excitability and reduces the frequency of sporadic seizures, as well as making the central nervous system more resistant to stresses and insults.
So, what is a Keto diet?
Adhering to a ketogenic diet involves putting one's body into a state of nutritional ketosis. This means that instead of relying on glucose for energy, the body relies on ketone bodies, which are produced by the liver from stored fat. As such, the body has a greater requirement for fat consumption via the diet. Classed as low carbohydrate, high fat and moderate protein, the exact proportions of each macronutrient will vary person-to-person, but advocates of the diet recommend that just 5-10% of a person's daily calorie intake comes from carbohydrates. This equates to 20-50 g a day.
1.1 What to eat
Those in favour of the keto diet are quick to reassure that the majority of fats can be obtained from unsaturated sources, in other words,the good fats, found in olives, avocados, nuts and seeds, and it is certainly true that making sure your diet contains some of these is beneficial for overall health. However, too much fat can be detrimental, particularly when it is the saturated type found in lard, butter, coconut oil and palm oil. These staples can rapidly become an integral part of a ketogenic diet, as they are a simple means of boosting fat consumption. The danger of this is that saturated fats are known to increase cholesterol levels, which, in turn, raises the risk of heart disease.
Protein is permitted, in moderation, but another issue with this diet is that it does not discriminate between types of protein. This means a lean, organic chicken breast is given the same nutrient weighting as an equal quantity of processed bacon, which is rich in saturated fat.
Keeping carbohydrates to a minimum means restricting the amount of pasta, bread, oats and cereals that are consumed. Sugars, either refined or naturally occurring, such as those found in honey, should also be avoided. Many fruits are rich in carbohydrates, so most followers of this diet restrict their intake to a small portion of berries. Carbohydrate-containing vegetables should also be avoided and replaced with non-starchy vegetables, including leafy greens (kale and spinach), broccoli, asparagus and cucumbers.
1.2 The positives
A 12 week study designed to investigate the proposed benefits of the keto diet when compared to a normal 'mixed' diet was performed using military personnel. Over the course of the study, participants saw a reduction in body mass and visceral fat, as well as a 48% improvement in insulin sensitivity. There was no reduction in physical performance.
Those who are pro-keto suggest a potential role for the diet in the management of some chronic conditions, including diabetes; a fact supported by the aforementioned study. This makes sense since carbohydrates are essentially sugars. Therefore, reducing carbohydrate intake will inevitably improve insulin resistance.
1.3 The negatives
Aside from the cardiac-based risks associated with a diet rich in fats, other problems associated with the keto diet are nutrient deficiency, constipation, increased stress on the liver and kidneys and heightened confusion and irritability, characterised as 'brain fuzz'.
In addition, to continue to see the benefits from a dieting perspective, a state of ketosis must be maintained, which means low carbohydrates consistently.
2. Paleolithic - 'Paleo' - Diet
Considered to be the world's most popular diet in 2013, and still highly favoured by celebrities and diet and lifestyle bloggers, the paleo diet has a simple concept; "if a caveman didn't eat it, then neither should you.'' Broadly speaking, it takes the diet of our hunter-gatherer ancestors and applies that to modern day life.
2.1 What to eat
Included on the list of 'good' foods are meat, fish, eggs, seeds. nuts and healthy fats. With the emphasis being on good quality, organic (if possible) ingredients. Food that is prohibited includes refined sugar, flour, margarines, trans fats and anything processed. This includes food marketed as 'diet' or 'low fat'. One of the most contentious points with this diet is the inclusion of dairy, legumes and grains in the list of foods to be avoided.
The diet is naturally low in carbohydrates, which can make adhering to it a challenge for athletes.
2.2 The positives
Adopting the paleo approach to eating and thinking, can be considered to be more of a healthy lifestyle change than an actual diet. If followed carefully, it is sustainable and the core message is strong; whole foods are good, processed foods are bad. It does not involve calorie counting, although people that adopt it generally consume fewer calories and find they are full up sooner.
Whilst, the diet in its purest sense does not include dairy, most participants today adapt it slightly for their needs and some now choose to include good quality full fat milk.
Scientific studies looking at the paleo diet are a little limited, but those done to date do show a tendency towards weight loss, improved glucose tolerance and reduced cardiovascular risk factors. This has led to the suggestion that this diet could be used in the management of metabolic disorders, reducing hypertension and improving insulin resistance. When this diet was compared to various other weight loss programmes, participants were found to have positive psychological characteristics and improved self esteem.
2.3 The negatives
Despite its widespread use over the past decade, this diet remains controversial amongst healthcare professionals. One of the major issues with the diet is that is it ‘over-hyped and under-researched’. Claims that it reduces the risk of autism, mental health issues and dementia, remain completely unfounded. The scientific studies performed to date have typically only covered a short time period (up to 3 months) and they have very small participant numbers, making drawing significant conclusions difficult. The only long-term study, which looked at the paleo diet over a 24 month period, found very few differences between it and a diet that followed standard nutritional guidelines.
Staunch followers, who opt to cut dairy out of their diet completely, are likely to become calcium deficient. In fact, some are getting less than 50% of their recommended daily intake, which will significantly increase their risk of developing osteoporosis.
Another drawback to this diet, is the financial aspect. With an emphasis on good, high quality ingredients, it has been suggested that the paleo diet is up to 10% more expensive than a standard diet.
3. Alkaline Diet
The basic principle of the alkaline diet is that our bodies function best at a pH that is slightly alkaline, 7.35-7.45. Therefore, by reducing our consumption of foods that create acidity, we are optimising the condition of our body.
3.1 What to eat
Fresh fruit and vegetables are the major component of this diet. Organic produce is recommended and followers of the diet are advised to investigate the type (and pH level) of soil their food is grown in. Alkalising foods include Brussels sprouts, kale and sweet potatoes. Food that should be avoided include eggs, processed foods and refined sugars. Dairy is limited to yoghurt and kefir, as these have probiotic activity. Caffeine and alcohol should also be avoided.
3.2 The positives
When adopted in moderation this diet actually encompasses good, old-fashioned, healthy eating. Reducing the intake of processed foods will naturally lower sodium consumption; excessive salt raises blood pressure, increasing the risk of heart attack and stroke. Eating more fruit and vegetables and cutting back on sugar and alcohol consumption will also improve your overall health. There is no calorie counting, so adhering to the alkaline diet is relatively straightforward once you know what food is and is not permitted.
The diet is said to lower inflammation, improve metabolism and reduce chronic pain. However, relief from chronic back pain was only actually achieved when patients were given alkaline supplementation, suggesting that diet adaptations alone may be insufficient to have a physiological effect.
This diet has proven to be successful for sportspeople, enabling them to prolong their careers.
3.3 The negatives
The biggest problem with this diet is that it relies on information that is factually inaccurate. It claims that it will help to balance the blood pH level; however, it is very unlikely that a change in diet will alter your blood pH, as this is closely regulated by the body's own internal systems. The pH of the urine may alter because it is a waste product, but contrary to what some suggest, this is not indicative of what is happening in the blood.
The alkaline diet claims to be anti-cancer as some studies have shown that cancer cells thrive in an acidic environment. It is proposed that by consuming alkalising foods, the conditions for cancer cell growth are made more inhospitable. However, these studies were limited to cancer cells grown in a petri dish and, as such, are not indicative of the growth of tumour cells in the complex multi-system human body.
Another misconception is in relation to the Acid-Ash hypothesis, which claims that this diet will protect bone density. The theory is that consuming a typical Western diet, rich in protein and grains, but low in potassium, causes metabolic acidosis. The Acid-Ash hypothesis states that this acid overload is counteracted by the release of salts, specifically calcium from the skeleton into the circulation, rendering people at risk of developing osteoporosis. Advocates of the alkaline diet claim that fruit and vegetables provide a supply of organic molecules that can be metabolised to bicarbonate and thereby protect the skeleton from excessive calcium loss. This hypothesis makes the assumption that excess urinary calcium correlates with a direct loss in skeletal calcium; there is no scientific evidence to support this. There is also no direct evidence that abiding by an alkaline diet will prevent calcium loss and protect bone density.
It is a pity that such sweeping generalisations and dubious science are used to promote this diet because in its most basic form, it is a good model to live by. Eating a diet low in processed foods and high in fruit and vegetables could benefit everyone.
4. Intermittent Fasting
Not so much a diet, as a change in eating habits; intermittent fasting is defined as periods of voluntary abstinence from food and drink. The theory behind intermittent fasting is that, as humans, we evolved in environments where food was sometimes scarce; thus, we already have the compensatory mechanisms in place to protect our physical and cognitive abilities when food reserves are low. There are many variants of the approach now, with the theory being that people can pick the style of fasting that best suits them:
- Complete fasting every other day
- 70% energy restriction (reduced calories) every other day
- Limited to 500 - 700 calories for 2 non-consecutive days every week (also known as the 5:2 diet)
- Time restricted feeding. Fasting for between 14 and 20 hours each day.
4.1 What to eat
One of the major benefits of this diet is that when not fasting, a normal diet can be consumed. This means that no food types are explicitly prohibited (or recommended). For those that attempt time restricted feeding, the same number of calories may be consumed daily, but the timing of meals is altered. Benefits will be seen if these changes make the diet more metabolically favourable. Those on a 5:2 type diet will, on average, see that their weekly calorie intake falls by approximately 25%, suggesting that on the 5 regular days, they are not excessively eating to compensate.
4.2 The positives
Intermittent fasting is one of the only modern diets where the pros seem to outweigh the cons. As a means of losing weight, it seems to work as well as traditional calorie counting diets. It regulates insulin resistance and helps to maintain glucose homeostasis. When calorie consumption is low or negligible, the body uses up its glycogen stores and starts to generate ketones for energy.
Intermittent fasting has been demonstrated to protect against metabolic conditions, such as diabetes and cardiovascular disease. Much of the work to date has involved animal studies, which for obvious reasons cannot be directly extrapolated to humans. However, these preliminary studies show that intermittent fasting increases the resistance of the brain and heart to stress; as well as slowing the progression of neuronal dysfunction in disease models of Alzheimer's, Parkinson's and Huntington's. This highlights the need for further, longer-term human studies to see how these results correlate in real life.
People that follow a modified fasting approach, such as the 5:2 diet generally report an overall improvement in mood, with a reduction in anger and tension and an increase in self-confidence. Compliance to the diet is generally high and these sorts of diets are thought to be easier for obese people to stick to than continuous energy restriction.
Intermittent fasting, performed correctly, is not harmful. Whichever regime is followed seems to result in some weight loss and the evidence to date suggests that it is an effective, non-pharmacological approach to improving overall health.
4.3 The negatives
Studies have yet to identify what the optimal fasting regime is, for example, how long to fast, whether to fast on consecutive days or not, whether to implement specific calorie restrictions or a total fast. Further, long term studies on humans are required, with the aim of determining whether the many benefits seen in animals are replicated in man.
Initial adaptation to fasting can be difficult. Some people experience bad moods, dizziness and fatigue as their bodies adjust to using ketones for energy. These effects should be short term.
There are a few groups of people for whom intermittent fasting is not appropriate. Those already taking antidiabetic medication should not fast as they will increase their risk of hypoglycaemia. Pregnant and breastfeeding women should also avoid fasting. Regular periods of fasting can disrupt the menstrual cycle due to fluctuations in hormone levels; therefore, those hoping to conceive may wish to avoid intermittent fasting.
5. Carb Cycling
Ideal for those who enjoy carbohydrates too much to avoid them all together, carb cycling involves adjusting your intake on a daily, weekly, or monthly basis. Examples of each are given below:
- Daily. Limit carbohydrate intake at breakfast time and eat normally for the remainder of the day.
- Weekly. Two days of high carbohydrates, low fat; two days of moderate carbohydrates; three days of low carbohydrates, high fat. Protein intake remains consistent.
- Monthly. Four weeks of low carbohydrates, followed by one week of 'refeeding' with a high carbohydrate diet.
5.1 What to eat
This diet is less about what you can eat and more about when you can eat it. Carbohydrates are permitted at predefined times. The important thing is to avoid unhealthy variants; those following the diet should ensure that during 'high fat' periods, the majority of their dietary fat consumption comes from unsaturated sources, such as fish, avocados, nuts and seeds. Avoiding saturated or trans fats, which are rich in hydrogenated products, will reduce the risk of high cholesterol levels. Carbohydrate intake should also be regulated; preferred sources are whole grains, vegetables, fruit and legumes. Refined carbohydrates, such as sugar-sweetened beverages, pastries and white bread are not recommended.
5.2 The positives
Those who alternate between periods of low carbs and periods of high carbs have the potential to benefit from both states. The flexibility and the lack of complete avoidance of any one macronutrient makes this diet easier to adhere to for some people, increasing the likelihood of long-term success. There is also a psychological benefit to not completely eliminating certain food types.
The benefits of a low carb diet include improving insulin sensitivity, lowering cholesterol levels and, therefore, reducing the risk of developing cardiovascular disease. A small study that looked at obese patients with type 2 diabetes who adopted a low carb diet for two weeks, not only saw improvements in blood glucose levels, but paticipants also lost weight due to reduced calorie intake. However, this was a very small scale study and further work is needed to validate this theory.
Using carbohydrates strategically means scheduling high carb intake around times when the body needs extra energy. Athletes use carb cycling to maximise their performance. They overload on carbs on the days they are training in order to replenish the muscles' glycogen supply and prevent fatigue.
These positive indications are encouraging, but can daily fluctuations in carbohydrate consumption really make a difference? The somewhat surprising answer to this question is, possibly yes. Normal recommended guidelines stipulate that a diet comprising 55% carbohydrates, 30% fats and 15% proteins is ideal. A recent study, which only considered breakfast, compared this standard diet to a low carb, high fat diet (<10% carbohydrates, 85% fats). Lunch and dinner was the same for both groups. The low carb, high fat group had reduced postprandial hyperglycaemia and improved glycemic variability. They were also reportedly less hungry as the day progressed, suggested that calorie intake throughout the day would be lower. Work such as this, could have a large impact on the health and wellbeing of patients with type 2 diabetes.
5.3 The negatives
It could be argued that this is not a diet as such and, following the recommendations precisely, will not guarantee weight loss. People do lose weight, but usually as a result of consuming fewer calories.
The theory behind the plan is good, but validated research is still lacking. The diet aims to exploit the benefits of a low carbohydrate eating plan, alongside intervals of carb loading, utilised to good effect by high performing athletes. It is still not clear what the optimum schedule is, or, in fact, if this will alter from person to person. There is also the possibility that this diet will only really benefit serious athletes and that alternative approaches are better for non-athletes.
It can take time to fine tune and individualise the diet and, this can lead to confusion and low adherence rates for those who want a simple formula to follow.
Over the years, the concept of what makes an ideal body shape has changed. One thing that has, however, remained consistent is a manipulation of one's dietary consumption with a view to obtaining the ideal body shape. The word diet, referring to the obtainment of regular nourishment from food and drink, has been in existence since the 13th Century; however, dieting as a concept and a means of losing weight was first proposed by Willliam Banting in 1863. He advocated a low carbohydrate, low calorie eating regime. His ideas are still available in print form today in his book entitled, "Letter on Corpulence". It is quite telling that, over 150 years later, many modern diets still advocate the extensive benefits of reducing carbohydrate intake.
The list of diets in this article is far from exhaustive; there are many different types and variants. Some that function on a membership-type basis, where you sign up to a programme and, in return, receive recipes and other resources; others, that exploit the principles of vegetarianism or veganism to promote healthy eating.
The purpose of this article is not to condemn all modern diets. As our scientific understanding of the human body and its interaction with macronutrients grows, we can, and should, adapt the way we eat to achieve a healthier lifestyle. The key is to select carefully which plan to follow; choose one which suits your lifestyle and try not to deprive yourself of everything that you enjoy, as this reduces your likelihood of adhering to the diet long-term. Examine the proposed benefits of a particular diet and bear in mind that not everything you read will be completely accurate. Ensure that you are not consuming anything that could cause you harm or putting your health at risk by starving your body of vital nutrients.
Above all else, it is worth consulting a healthcare professional before implementing any dietary adjustments, particularly if you have an underlying medical condition.
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