Recently, I was asked by a US colleague about what diet do I recommend to my patients. The truth is I don’t really know what to say to them anymore. In the past, I used to say eat a ‘heart-healthy’ diet. However, since the scandal surrounding the low-fat ‘heart-healthy’ recommendations having been exposed as not being evidence-based and being heavily influenced by the food industry it is difficult to know what diet to recommend. I even have serious doubts about the so-called Mediterranean diet, which is a very nebulous entity and in all likelihood was invented as a marketing tool for the olive oil industry. You will find it difficult to find a place that eats a typical Mediterranean diet.
I have therefore reverted to evolutionary medicine when it comes to my dietary principles, which can be summarised as five principles.
- Eat socially
- Eat real food, i.e. avoid processed and ultra-processed food
- Eat local
- Eat seasonally
- Eat mindfully
Eating is or at least it should be a social activity. Meals should be about sitting down with family, friends and colleagues and enjoying each others company. A lot of our rituals, religious and non-religious, revolve around eating; often in the form of feasts. If your diet prevents you from using meal times as a social activity it will impact on your social capital.
If I don’t eat my evening meal with family and/or friends my day feels strangely incomplete. The same goes for our ritual Sunday family roast. I look forward to preparing the Sunday roast and enjoying it with my family; a week without our family roast is an incomplete week.
Eat real food
Real food is knowing its provenance and being able to identify what it is. In general, real food is whole, single-ingredient food. It is mostly unprocessed, free of chemical additives, and rich in nutrients. In essence, it’s the type of food we ate exclusively for thousands of years and its the type of food that drove our evolution. The types of real food that are processed include fermented, cured and dried foods. The fermentation process is used to preserve food when they are abundant for times of scarcity and to help with digestion. For example, the move from eating sourdough or slowly fermented bread using a wild culture to modern ultra-processed bread fermented very rapidly is hypothesised to be one of the reasons for the rise in gluten sensitivity. The wild sourdough culture includes not only yeast but symbiotic bacteria that breakdown gluten differently to monoculture yeast used in industrial bread production.
However, the main problem with processed and ultra-processed food is what it does to our metabolism.
Complex (unprocessed) carbohydrates tend to have a low GI index (unless you juice them), i.e. they release their sugars slowly and induce less insulin. In comparison, processed foods are high in carbohydrates and have a high glycaemic index (GI). High GI foods don’t need much digestion and hence release their sugars very quickly, which are rapidly absorbed, which then stimulates high levels of insulin, which activates the body to process the high sugar levels. We now know that the insulin is not only produced for sugar in the here and now but also as an anticipatory hormone. The insulin response expects sugars to be absorbed over several hours, which is what happens with low GI foods or real food.
The excess insulin in response to high GI, or processed foods, then lowers your glucose levels causing relative hypoglycaemia. This occurs because processed sugars are rapidly absorbed from your intestine without a long absorption tail that we see with low GI complex carbohydrates. The low blood glucose after high GI foods triggers a hunger response and drives one to seek more food. As this occurs between meals it results in snacking between meals. In the very well done study below when people ate a diet high in processed and ultra-processed foods they consumed over 500 calories more a day compared to the period when they were on a real-food diet. This extra calorie intake would have almost certainly been driven by the excess insulin-induced hypoglycaemia from high GI foods and resulted in more weight gain.
Eat local is about the environment and supporting your own farmers. The economic and environmental arguments for this are well-rehearsed. Why eat foods with a large carbon footprint when you can eat local sustainable foods. We always try and buy local, but it is not always possible because the agribusiness is now a global industry.
For the evolutionary medicine purist, this makes sense. I have written a previous post on why it is important to eat seasonally, particularly in relation to carbohydrate metabolism. Interestingly a lot of chefs understand this concept and will only present seasonal menus in their restaurants. I suspect the reason for this is they understand the importance of the seasonal cycle to our metabolism. We pay a massive price by ignoring the seasonal rhythms in relation to our diets and metabolism.
Pay attention to what you eat and think about it in the moment, i.e. your own thoughts and feelings about the food you are eating and the impact this is having on those around you and the environment. Being mindful will challenge you when you are eating for comfort and not because you are hungry or being sociable. This will also allow you to adopt an environmentally friendly diet.
Mindful eating is compatible with the slow food movement which envisions a world in which all people can access and enjoy food that is good for them, good for those who grow it and good for the planet. The slow food movement is based on a concept of food that is defined by three interconnected principles: good, clean and fair.
GOOD: quality, flavoursome and healthy food
CLEAN: production that does not harm the environment
FAIR: accessible prices for consumers and fair conditions and pay for producers
So, in summary, I don’t think there is a right answer when it comes to diet. However, if you adopt some of the basic principles above your diet will contribute to your overall wellness.
Hall et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab, 30 (1), 67–77.e3 2019 Jul 2.
We investigated whether ultra-processed foods affect energy intake in 20 weight-stable adults, aged (mean ± SE) 31.2 ± 1.6 years and BMI = 27 ± 1.5 kg/m2. Subjects were admitted to the NIH Clinical Center and randomized to receive either ultra-processed or unprocessed diets for 2 weeks immediately followed by the alternate diet for 2 weeks. Meals were designed to be matched for presented calories, energy density, macronutrients, sugar, sodium, and fibre. Subjects were instructed to consume as much or as little as desired. Energy intake was greater during the ultra-processed diet (508 ± 106 kcal/day; p = 0.0001), with increased consumption of carbohydrate (280 ± 54 kcal/day; p < 0.0001) and fat (230 ± 53 kcal/day; p = 0.0004), but not protein (-2 ± 12 kcal/day; p = 0.85). Weight changes were highly correlated with energy intake (r = 0.8, p < 0.0001), with participants gaining 0.9 ± 0.3 kg (p = 0.009) during the ultra-processed diet and losing 0.9 ± 0.3 kg (p = 0.007) during the unprocessed diet. Limiting consumption of ultra-processed foods may be an effective strategy for obesity prevention and treatment.