My ‘Four Diet Dictums’:
1: All Diets work in the short term.
2: All Diets work equally in the short term.
3: All Diets fail in the long term.
4: All Diets fail equally in the long term.
This is my interpretation of the science. It may seem nihilistic, but I think it’s empowering.
For example, if you want to shed weight for a short-term body-image project (e.g. for an event, or summer) then just pick a Diet that suits you – they all work. If you like meat then choose a high-protein low-carb Diet; if you like carbs then choose a low-fat Diet; if you like everything and are prepared for regular depravation, try the 5:2 Diet, and so on. If the diet plan suits you, then you are more likely to succeed.
But, be aware that up to 95% of dieters who are successful at shedding weight will regain that weight (often more). In fact, the most interesting feature of Diets is their massive failure-rate. You might even wonder if they are designed to fail, so that a frustrated dieter will try or need another one. It is a diet industry, after all (est. worth $60 billion annually). When weight regained is greater than weight lost, cycles of repeat dieting (yo-yo dieting) can result in long term weight increase. Plus, Diets can be harmful (food anxieties, nutritional disruption, decreased energy levels, issues of self-respect and quality of life) and, in some cases, can evolve into eating disorders.
Biology also has an inevitable part to play in the failure of Diets (too often the dieter is blamed, or blames themselves, which is wrong). The body regulates its weight remarkably well in the longer term, given daily fluctuations in eating and physical activity. On average, it maintains its weight to within 0.2 to 1 kg per annum (requiring regulation of caloric digestion to better than 0.5% accuracy), although unfortunately it favours an annual surplus in this range (yes, despite this precision, weight will drift north).
The body has multiple mechanisms that work in concert to maintain this level of control. And then, unexpectedly, it finds itself in the maelstrom of a Diet. At first, it fiercely resists depleting its cherished fat stores, but finally has to give in and weight loss ensues. The body then switches to its default survival-mode. Some known mechanisms are: resting metabolic rate falls below what would be expected for the new weight – this favours weight gain; insulin sensitivity changes, in a way that favours fat storage and weight gain; hormonal balances change (between weight gain and weight loss signallers), in a way that favours weight gain, and; the brain region that oversees all this (hypothalamus) releases chemical messengers that favour weight gain. The worrying thing is that these adjustments can persist for at least a year after the diet. Then, there is a person’s genetic set-point to contend with. From the perspective of these systems, a sudden loss of weight is a potential disaster that needs to be corrected. So it is no surprise that Crash Diets soon crash.
But none of this means we should surrender to the inevitability of weight-gain either. Our evolutionary biology may be working against us and our hereditary biology may be working against us, but we have also evolved something that can work for us – our brain. We can choose to adjust our behaviour to suit this modern eating environment that our biology didn’t predict and is not prepared for.
An approach might be by stealth, to avoid triggering a panic attack in the weight-monitoring hardware. Start slow, maybe replace one food item with something else. Then, don’t do anything for a while, get used to this change then make another. Don’t fret over this, it is a gradual process and should be unhurried. It is more likely to work if it is unhurried. After a while, think about similar ways to increase physical activity. You might find this happens as a natural consequence of losing a little weight and feeling healthier. Let each improvement lead to another improvement and the effect, slow to begin with, can snowball. Because you are adjusting along the way, your new lifestyle is likely to be sustainable for the decades ahead and the body has the chance to accept your new weight as a new set-point.
I don’t rule out that for some (I suspect <5%) a Diet might kick-start longer-term weight management, however it could also kick-start compensatory mechanisms that make weight management more difficult to achieve and even result in weight gain. Brand-name Diets that promise fast results come with these traps. What is best for our health and quality of life is a slow and sustainable result.
UPDATE 13/5/2016: This post is about Diets that restrict calories or that try to change the balance of calories-in to calories-out. These Diets fail. At the time of writing, I was not aware of the existence of a more scientifically-based approach. It is called the ketogenic diet and, rather than restricting calories-in, or recommending exercise to increase calories-out, it changes the balance between macronutrients (carbohydrate, fat, protein) without changing total calories. You can read an updated account of why calorie-based diets fail here. And about the ketogenic diet here.
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