The traditional theory linking modern processed food to obesity is that these foods are packed with calories and taste delicious, so we overeat them and take in more calories than we burn, storing the excess energy as fat. But weight gain and obesity are not under conscious control. If our weight anchor is stable, then we will subconsciously compensate for overeating by increasing our metabolism to burn off more energy, and decreasing our appetite to take in less. Our weight controls itself in a similar way to our hydration: if we drink too much water, the body compensates by passing more urine, we don’t suddenly start retaining water.
So, why does our body not regulate its weight when we take in processed foods? Why do processed foods seem to raise our weight set-point and shift our weight anchor upwards? Sugar, fructose and vegetable oils are three of the most common additives to our diet that scramble our brain’s weight-control centre and signal to our brain to gain weight.
Modern food contains lots of these three additives. Individually, each of these factors can derail our metabolism, sending a signal to our bodies to gain weight. When the signals are combined within an ultra-processed diet, they can be overwhelming and lead to that hopeless feeling many of my patients describe, of losing natural weight control.
Take sugar. Our weight is controlled by the hormone leptin, which originates in our fat cells. The fatter we are, the more leptin is signalled to the brain, and the brain compensates for this by reducing appetite and increasing metabolism.
Let’s repeat this because it is a crucial insight in understanding our weight: if we gain fat, then more leptin is produced. Leptin is sensed by the brain, and the brain understands we have more fat than needed, so it decreases our appetite and increases our metabolism, leading to the weight gain being controlled.
However, sugar and foods containing refined carbohydrates (which have the same effect as sugar) such as wheat (bread, cakes, biscuits and pasta) can block the protective leptin feedback mechanism via the hormone insulin. The more of these types of foods that we eat, and the more often that we eat them (via our new snacking culture), the higher our insulin response will be. Insulin is the hormone that then blocks the leptin signal, meaning the brain can no longer sense how much fat is present in the body and therefore cannot compensate for the weight gain caused by excess calorie intake from our delicious and addictive UPFs (ultra processed foods).
Historically, humans would never have encountered foods containing so much sugar and would never have eaten these foods so regularly, so the leptin signal would always have kept on working to keep weight stable. However, there is an exception to this rule in some hibernating or migrating species of animals, who rapidly gain weight in response to a signal from nature. Unfortunately, this signal also works in humans, and it hides in processed food.
However, once you know which food to avoid and what to swap in you can help your body reactivate your normal weight-control mechanisms and reap the benefits of fresh, healthier foods.
What to avoid
All processed foods whose main ingredients are artificial fructose, sweeteners and vegetable oils.
Refined carbohydrates such as wheat flour (it’s OK in cooking as an additive to sauces and as a crispy coating).
Vegetable oils, including sunflower oil, rapeseed oil, corn oil, cottonseed oil, safflower oil, ‘vegetable’ oil, canola oil (ignore the ‘high in omega-claim’ – it disappears within thirty seconds of heating), margarine, ‘easy spread’ fake butter and shortening.
What to eat
Remember that fresh vegetables, particularly leafy green and brightly coloured ones, infuse your body with phytochemicals, those anti-inflammatory and life-extending antioxidant messages from our plant friends. Taking in most of your carbohydrates via these types of vegetables is highly recommended. If you do this, your body will reactivate your normal weight-control mechanisms and excess fat will be sensed and shed.
Red meat is not bad for you. It is full of health-giving natural saturated fats. These fats do not spike insulin levels and do not cause obesity. Grass-fed meat (beef and lamb) is better as it will have higher omega-3 levels.
Pulses and beans are a fantastic source of healthy high-protein calories and can be used in place of typical staple carbs (rice, pasta, potato). Another often overlooked alternative to traditional carbohydrates are grains like buckwheat or quinoa. They are easy to prepare, tasty, have lower effects on insulin, and feature higher protein and nutrient contents compared to traditional carbs. If you switch to these foods instead of rice, your body will respond favourably.
The best fruits to consume are berries, which are full of phytochemicals and low in fructose sugar.
If you consume dairy products, natural yogurts and cottage cheeses are high in protein, calcium and B vitamins. These are great foods to start your day with.
Canned fish such as tuna, salmon, sardines or mackerel (in tomato, and not oil) are convenient snacks that are full of nutrients, particularly omega-3.
Instead of vegetable oils, stock your pantry with extra virgin olive oil, butter, coconut butter and clarified butter (ghee).
If you find you crave unhealthy UPFs, crave surfing could help. When a craving to perform an addictive and unhealthy habit arises, ask yourself how you really feel – question where the craving has come from. By thinking more deeply about the craving and why it has arisen, you can be more mindful in your response – many cravings will pass after a few minutes.
Concentrate on your breathing and be mindful of how the craving feels, observing the intensity of the craving as it gets bigger and bigger, like a wave, until it peaks and then crashes.
Dr Andrew Jenkinson is the author of How to Eat (And Still Lose Weight): A Science-backed Guide to Nutrition and Health, out now (Penguin Life, £18.99).