I like watching my dog eat – there is a certain uncomplicated joy in the way he munches his food, profoundly trusting in us to provide him with healthy nutrition.
Humans have the same need for nutrition, of course – but the major difference is that we have infinitely more tasty options and histrionic diversions. This inevitably causes many people to overindulge, making more profits for the food industries, which then create even more alluring options. It is the contemporary cycle of food consumption, wildly exacerbated by the vast communications infrastructure of the modern world. Such careless indulgence inexorably raises health issues, accompanied by guilt and worry which then usually lead to some form of dieting – and therein lies an unusual problem.
When I go to pet shops, the dog food options are limited. I can get food for big dogs, small dogs, old dogs, young dogs, dogs with skin conditions, overweight dogs – and that is about it.
By contrast, the “healthy diet” options for humans appear infinite, with a new diet fad appearing almost daily. All these diets are self-declared “miracles” by “experts” in white coats – and there is ALWAYS someone featured expressing gratitude for some new diet which “worked when all others failed”. Then there are the books, packaged meals and subscription plans – dieticians need to make a living too.
After perusing (very) many dietary fads (or “plans” as they prefer to be called), I thought it useful to condense all these plans into a couple of pithy pages. Diet plans are decomposed into their underlying premise rather than individually analysed (as there are just too many diets) – by premise, I mean division into categories such as calorie restricted, food group limited, time restricted, supplemental, combinational or fanciful. Then the claimed benefits and objectively-determined attributes of each category will be summarised.
Not all diet plans are about losing weight; some claim to promote longevity or reduce skin problems, others seemingly offer better brain function, improved cardiovascular capacity, pain management, or even enhanced physiques, etc – the variants are endless. Many diet plans cross category boundaries (eg. most weight loss diets are calorie-restricted in some way), so many plans adopt the positive and negative attributes of more than one category. After reviewing so many plans, I simply needed a new way to look at how many fads claim to work and categorisation has significantly helped in understanding the concepts behind all diet plans.
It is also acknowledged that people are inherently different – not only genetically, but also in their underlying health, digestive capabilities (eg. differences in HGM, or human gastrointestinal microbiota), environments (eg. stress levels, work patterns, exposure to pollutants), income, cultural backgrounds and access to food options. As such, particular diet plans may have quirks which may suit certain people better than others – in short, it is extremely improbable that even a simple diet with a single premise (eg. weight loss) would work equally well across a large group of followers.
According to Time magazine, the expected dietary hits for 2018 are the DASH Diet, Mediterranean Diet, Flexitarian Diet, Weight Watchers, MIND Diet, TLC Diet and Volumetrics. I could have picked other magazines and they would have confusingly different lists of top diets – that is why it may be worthwhile to look at diet plans in a new way.
If you are curious about the acronyms, DASH means Dietary Approaches to Stop Hypertension, MIND stands for a mix of Mediterranean and DASH and TLC is Therapeutic Lifestyle Changes.
Not all diet plans are about losing weight; some claim to promote longevity or reduce skin problems, others seemingly offer better brain function, improved cardiovascular capacity, pain management, or even enhanced physiques, etc – the variants are endless.
If you are still inquisitive, the DASH diet claims to help alleviate high blood pressure and is similar to other food group restricted diets but with added emphasis on reducing salt intake. The MIND diet is another food group restricted diet claimed to slow cognitive decline and the TLC diet focuses on cholesterol reduction via a combination of calorie restriction, food group restriction, exercise and in some cases, drugs as well. You will understand more from the essence of each category below.
And so we start with categorisation of diets based on their major characteristics. As mentioned, many diets stray into multiple categories and the significance will be obvious later.
Category 1 – Calorie restricted diets
These diets basically limit the number of consumable calories. The premise is reducing the intake of calories inhibits the body’s proclivity to store excess calories as fat. Also, eating fewer calories means that the body will switch to burning stored fat, thereby causing weight loss.
In practice, this approach is often effective in the short term, because the logic is irrefutable. However, the strain of reducing food intake means that the body might adopt a slower metabolic rate – this means that the rate of weight loss due to burning stored fat may slow after a while. Reducing calories usually also messes with the hormonal interplay for managing hunger, causing wild mood swings and making it common to develop severe food cravings – this is the primary reason why many people give up calorie-reduced diets after a while.
One important thing to note is that not all calories are equal – much depends on whether food has been cooked or not. For example, weight-for-weight, cooked carrots have far more digestible calories than raw carrots. This is the Thermic Effect of Food (TEF) where calories from raw, uncooked food need more energy for digestion while calories in cooked food are far easier to absorb – hence cooked foods may introduce 15% to 35% more calories than the raw versions. Oddly, TEF is a significant point which is seldom mentioned by many calorie-restricted diets.
There is an interesting variant based originally on the diets of Okinawans. Normally, most food would have over one calorie per gram, but some diets specify consuming meals where the number of calories is less than the weight of the food in grams. This ostensibly can help improve longevity – at least, that is one hypothesis to explain the unusual ages of older Okinawans.
Category 2 – Food group limited diets
Food groups can vary depending on the diet plan – and general food groups are animal meats, fish, shellfish, plants, fruits, grains, sugars, dairy, etc. It may also extend to wider groups such as carbohydrates, fats, animal proteins, plant proteins, high-fibre foods, etc. Yet more groups may include organic produce, processed foods, low-fat, selected vegetable oils, specific vinegars, etc.
Certain diets specifically exclude or include only some groups. There seems to be no limit to the ingenuity of food groups invented to fit into many dietary plans, depending on the diet hypothesis proposed; eg. weight loss, health, longevity, etc.
Generally, if the food groups allowed in a plan are diverse enough and contain adequate nutrients and fibre, then there are no real concerns. However, many diets specifically exclude important groups – for example, some high-protein diets include mostly meats while excluding carbohydrates and fruits. This may be tolerable for people in good health but may not be the best option for someone with chronic constipation. Also, little attention is paid to what happens to the HGM when drastically switching to new food groups.
Many diets are often presented as “one size fits all” – however, like shoes, that is seldom true. It also matters if the permitted food groups are items you enjoy eating.
Category 3 – Time restricted diets
Applying time restrictions is a more recent development, and several diets arose from research at US universities several years ago where heavily restricting calories for a few days was found to boost the immune system significantly. The reasons for this effect are unclear but may have been an adaptive mechanism to boost body defences during ancient times of food shortages. Palaeolithic humans were nomadic hunter-gatherers and during times of famine, they wandered to new lands and thus encountered different microbial flora – so an improved immune system would have been beneficial.
Time-deprived diets require periods of curtailed calorie consumption (eg. two days each week or a few days a month) – and are generally proposed as a way to boost health and longevity.
Some newer alternative intermittent fasting (IF) diets restrict the time during the day when food can be eaten; eg. circumscribing eating to only an eight-hour window each day. Why this should work is not scientifically explained – perhaps such a plan would avoid snacking continuously during the day. In mice experiments, it was claimed that IF provided more time and resources for the test mammals to repair their bodies, though the diurnal (daily) feeding cycle for mice is completely different from humans. There were also some minor IF studies on humans but the sample sizes were too small to be reliable.
One advantage of some time-limited diets appears to be no requirement for altering existing food habits (or even quantities), except during restricted periods.