The systems that regulate our food intake and fat stores are highly evolved and extremely complex. Australians are not becoming obese because of an outbreak of gluttony or a design flaw in the human body – the problem is the type of food we are eating.
The “law of satiety” (Doug Lisle) states that an animal in its natural food environment will eat just the right amount of food to maintain its body weight within a narrow range, neither starving itself unnecessarily nor becoming obese when food is plentiful. Kangaroos do not become obese and unable to hop when there is abundant green grass and parrots do not become too heavy to fly when their food is plentiful. Only a handful of animal species have a natural seasonal pattern of fattening up prior to periods of hibernation or migration and humans are not one of those species.
Our genes have changed very little in the last 10 000yr. We have the same physiology as our hunter gather ancestors who were well adapted for a diet based predominantly on high fibre, low calorie density plant foods. The consumption of wild game meat was irregular and may have reflected that our ancestors were survivors rather than omnivores. Modern processed foods and animal products provide calories that are hyper-concentrated beyond the capacity of our weight regulating physiology. The failure of our appetite mechanism to fully compensate for the calorie density of this food results in systematic overeating and gradual weight gain.
The transition to agriculture gave our ancestors a plentiful supply of starchy grains, legumes and tubers. This dietary pattern was still within the operating range of our weight regulating physiology and the farmers remained lean and healthy while they were eating their crops with little more processing than peeling, grinding and cooking. A diet based on minimally processed vegetables, grains and other starches does not cause obesity even when food is plentiful – forget the idea that obesity is a natural consequence of plenty, that’s just an excuse for modern diet.
Satiety, the feeling that one has had enough to eat, has a central role in weight control. The current nutrition dogma in Australia suggests that we “eat protein for satiety” and that way we’ll eat less and lose weight. Ironically some of the studies that found that meals higher in (animal) protein resulted in greater satiety, did not find that a higher protein diet was any better for weight loss, and you can be assured that a whole plant foods were not used for comparison. The idea that eating more animal-derived ‘protein foods’ will help people lose weight is inconsistent with real world observations. The research consistently finds that vegetarians are leaner, with those on the most plant-based diets, vegan, being leanest. The ongoing EPIC PANACEA study has found that meat consumption, particularly chicken, is associated with greater weight gain.
The main factor that gives us a feeling of satiety is the volume of food in the stomach. The stomach wall has stretch receptors which measure the degree of distension or fullness. There is also a complex array of receptors and hormones which measure the intake of protein, carbohydrate and fat – and for individuals these work extraordinarily well, but for most of us it’s the fullness of the stomach that’s most important. Studies show that people tend to eat the same volume of food at a meal regardless of the number of calories. Foods that provide more bulk for the same number of calories provide greater satiety and result in less calories being consumed at each meal. Conversely, eating more calorie dense (less bulky) foods leads to increased calorie intake and weight gain. There are over fifty studies that show this.
The following diagram illustrates the effect of bulk on stomach fullness. Each meal has the same number of calories, but differing bulk. It’s easy to see which type of meal leaves room for overeating.
Water and fibre bulk-up food and reduce its calorie density. Adding fat, and to a lesser degree sugar, adds a lot of calories but very little bulk. The food industry hyper-concentrates food by removing the fibre and water that give it bulk and adding fat and sugar. It is difficult not to overeat this hyper-concentrated food without strict portion control. Animal derived foods contain no dietary fibre and most have a moderate to high fat content. They are just as much a part of the problem as processed foods.
Most of the plant-based foods eaten in Australia have been hyper-concentrated by processing that removes fibre or adds fat and sugar. Our potatoes are fried in fat, our grains are refined and low in fibre and only one person in twenty meets the daily recommended minimum intake of fruits and vegetables. And while our obesity crisis worsens, our nutrition experts have been encouraging the public to add even more fat to their meals in the form of olive oil. Sugar is a source of hyper-concentrated calories but national sugar consumption has not increased over the last few decades.
Liquid calories are another important issue. Soft drinks, milk and fruit juices have a high water content but do not provide bulk and satiety. These foods contain little or no fibre and the water in them is rapidly absorbed in the gut leaving little residual bulk for satiety. Smoothies too, provide reduced satiety because, although the fibre is retained, it’s been disrupted by fine blending, and the chewing stage of digestion has been bypassed. Chef AJ suggests trying to eat your smoothie ingredients before they are blended to test out how much more filling they would be.
Dried foods have a higher calorie density and provide less satiety because the bulk has been reduced by removing water. Dried fruits and baked whole grains are easier to overeat than fresh fruits and well-hydrated grain products such as cooked rice and pasta.
It is often said that the reason why most Australians are overweight is that we simply eat too much food – less than 20g of fibre and meagre quantities of fruits and vegetables is too much food? We suggest that the opposite is true – that Australians are not eating enough food – not enough of the whole plant foods that provide satiety. Many Australians are trying to eat in moderation but the food is hyper-concentrated. When we eat the right type of food, a healthy appetite is no longer undesirable. On the contrary, a big appetite supports the consumption of large amounts of nutrient rich, low calorie density whole plant foods.
Weight loss drugs and surgical procedures are crude hacks on a complex system – attempts to fix something that’s not broken – the problem is the type of food.
Page last updated 14 February 2016