Sun, Jan-05-20, 11:51
Why we eat too much: the new science of appetite (and what it tells us about losing weight)
Obesity is on the rise, and our approach to weight loss isn’t working. Dr Andrew Jenkinson explains why it’s time for a rethink
Dr Andrew Jenkinson was once as prejudiced as most people are about obesity. He thought those who tipped the scales at 20st but carried on eating regardless, often bingeing on calorific foods, were irresponsible and lacked will power. Indeed when a patient once walked into his bariatric clinic carrying a plastic bag full of sausage rolls, crisps and snacks, he told the man to take some responsibility for himself and go on a diet, he tells me a little sheepishly.
Today he thinks differently. His understanding of the science of hunger and weight means he appreciates being obese isn’t the lifestyle choice he once thought it was.
Yet we are in the grip of an obesity crisis.
A recent NHS report detailed how more than 56 per cent of adults are at increased, high or very high risk of chronic disease due to their waist circumference and BMI, with 26 per cent of men and 29 per cent of women being reported as obese.
When Dr Jenkinson trained as a surgeon it was initially in the field of laparoscopy, but so great was the demand for bariatric surgery that slowly it took over his practice.
For the past 15 years he has performed complex surgery on those seeking to escape the trap of obesity. And as scores of patients turned into thousands, the penny dropped. His patients weren’t lying when they said they had tried everything, when they said that they could lose weight but it was impossible to keep it off.
He realised there were scientific reasons why they were trapped in a vicious cycle of ~dieting and weight gain. And that the situation wasn’t helped by our poor nutritional guidelines, and an emphasis on counting calories.
The compelling evidence behind his ~Damascene conversion is presented in his fascinating new book, Why We Eat (Too Much). It will engross anyone who has ever struggled with dieting, but you don’t have to want to lose weight to read it. I admit as I turned the first page my mind was made up already about why some people eat too much. As a slim, active person I could be judgmental of those who weren’t. I knew I would need to be persuaded. And, I was.
It hinges on our current perception of obesity, even within the medical community, that weight loss is easy: simply restrict calories and go on a diet an increase exercise to expend calories.
“It’s a one-dimensional equation but my patients seemed to think it was a much more complicated situation, to such an extent that they wanted me to remove their stomachs,” says Dr Jenkinson, a consultant at University College London Hospital.
Their desperation made him think twice about whether it really was just a question of self-control.
By exploring the science behind hunger, he came to understand that when people say things like “I can’t control my hunger, I feel weak if I don’t eat”, or “I think I have a slow metabolism compared to other people I live with”, they are telling the truth.
Why diets don't work
Our metabolism isn’t under our control. It can vary dramatically depending on how much we eat. It’s not as simple as eating a Snickers, then pounding it off on the treadmill, because if that were true, the average person would be four stone heavier than 40 years ago. From 1980 to now in America calorie intake has increased by 500 calories per person per day, yet weight gain was only 0.5kg (1lb) per year.
The reason people aren’t heavier, says Dr Jenkinson, is that our metabolic rate has shifted to account for those extra calories, burning off more energy. Bear in mind that if we were to lie in bed all day and all night we would still use up to 70 per cent of the energy that we normally do, through breathing, heartbeat, temperature control and all our cells’ chemical reactions. Calorie burning isn’t purely about going to the gym.
Our metabolic variation is an example of how we achieve homeostasis; the body shifting to find its healthy neutral. Dr Jenkinson compares it to a person who drinks three litres of water a day and is constantly going to the loo, and the person who drinks barely anything and doesn’t.
In those who diet a lot, their weight set-point – the level of energy (fat) storage that our brain calculates is necessary for our survival – shifts. The more diets you’ve been on, the higher your weight set-point and the slower your metabolism, because your body wants to protect you.
“We’re survival machines,” says Dr Jenkinson. “Going on a diet sends a signal to the hypothalamus [which regulates hunger levels] that there’s a famine and that you’d better put on a little bit more weight for the future.”
And so it’s common for serial dieters to lose weight initially, plateau, and then put all the weight back on plus some extra.
Dr Jenkinson’s mission is to raise awareness of the damage that low-calorie diets can do to our metabolism.
“Most of my patients’ problems started when they started dieting. They were a size 10 or 12. And sort of OK. Then they started dieting.”
After a period of starving yourself, you’ve sent your body signals that it needs to be bigger. It wants two or three months’ worth of fat in case there’s a famine, and so you end up a size 14. “Going on a strict diet is training yourself for the weight-gain Olympics,” he says tartly.
The Pacific predisposition
Genetic predisposition plays a part, too. If your ancestors have gone through lots of famines then you might have been preselected for obesity.
This is evident in the Pacific Islands, home to nine of the top 10 countries for obesity. The islands were one of the last places on Earth to be inhabited by humans, probably around 1000BC. The journeys to get there were long and arduous. Not surprisingly, many did not survive the journey.
“There was therefore automatically a huge selection bias for anyone settled there,” says Dr Jenkinson. “Those people who had enough fat reserves before the journey, or those with metabolisms that could shut down in the face of starvation, had a much better chance of surviving the long journey. The sailors and passengers who did not have this insurance perished and did not have the opportunity to pass their genes on to the next generation.”
The consequence was a selection bias of people with good fat reserves, or efficient metabolisms surviving to colonise this distant part of the world. “It was extreme selective breeding,” says Dr Jenkinson.
There was no problem with obesity while the population consumed fresh, natural foods, but the recent introduction of a Western-type diet has played havoc with many Pacific Islanders’ weight and health.
As he tells me this, Dr Jenkinson is on his second coffee. I watch him heap sugar into it, just like he did with the first. When I draw attention to his habit, he admits that if he were obese and described his diet to a doctor they would say that was the reason he was fat. He likes chocolate and sugary snacks. “My dad’s slim and has an allergy to vegetables,” he says.
It’s frustrating but some people really can eat all the wrong things and not put on weight. The stark fact is we live in a time of extremely poor nutritional education, and if you’re predisposed to lay down fat, then you’re more likely to be one of the people who ends up walking through Dr Jenkinson’s door.
But how does that really account for people who weigh more than 20st? Are some people surely just greedy? Dr Jenkinson concedes that: “If you have a hedonic attachment to food you need to look to things like eating more mindfully.”
It’s not that simple though, because when they reach a certain level of extreme obesity, people develop leptin resistance. Leptin is a hormone that regulates your weight by telling the hypothalamus how much fat you have. If you develop leptin resistance then the brain senses a much lower leptin level than is actually present and interprets this as starvation.
“The people I see binge every single day because the disease has reached an extent in which the gas tank meter isn’t working any more and they constantly feel like it’s empty and have to constantly refuel,” says Dr Jenkinson.
The type of bariatric surgery he performs, a gastric sleeve, solves this problem by removing the part of the stomach that secretes ghrelin. Ghrelin is the hormone responsible for stimulating our appetite. If you have low ghrelin levels, you have a low appetite. His patients then typically crave less sugary, calorific foods, he says. But Dr Jenkinson wants to reach people before they consider surgery. For him, it’s what we’re eating that is really the root of the obesity epidemic. Nutritional advice in the early Eighties demonised cholesterol and resulted in the general population eating more grains, helping create our obesity crisis.
“It was supposed to be whole grains, but nobody did that – they were eating refined grains, which are essentially sugar. So the whole population’s insulin level went up and everyone got obese,” explains Dr Jenkinson. And when genetic predisposition combines with the environmental trigger of poor-quality diet, the result is weight gain.
So when many of us start our day with toast or sugary cereal, we’re immediately getting on board the sugar-spike roller coaster. By mid-morning you need a snack, then lunch, perhaps a can of Coca-Cola or some crisps in the afternoon. All day you experience these glucose ups and downs.
Added to this, Dr Jenkinson believes there has been a disruption to the cellular profile of essential fatty acids, omega-6 and 3, in our bodies in the past 40 years. We are eating far more omega 6 than 3, which is a problem because high levels of omega-6 can prevent the body from converting the omega-3. High levels of omega-6 have been shown to cause poorer insulin function, leading to an increase of insulin and a dulling of the leptin signal. The result? A higher weight-setting point and weight gain.
“The problem with omega-3, though, as far as the food industry is concerned, is that it causes food to go off and become rancid, which is actually a sign that it is food and not a manufactured food replacement,” adds Dr Jenkinson. And so the demonisation of natural saturated fats, like dairy and red meat, led to the increased consumption of highly processed, high omega-6 vegetable oil – “a totally unnatural food,” says Dr Jenkinson.
Interestingly, countries such as France that ignored the advice of the Eighties and carried on enjoying cheese, wine and meat in moderation, have avoided the problems besetting most of the Western world.
Ban calorie counting
Reading this, you might feel something akin to despair, but before you throw your hands up and exclaim, “well what am I supposed to do if I can’t go on a diet?” Dr Jenkinson says we can do the right things and lose weight. There are lots of lifestyle choices you can make starting today. It’s about having the right information. “If you’re predisposed to obesity and given the wrong advice, it’s hard to source the right foods, and bad food is cheap,” he says.
And of course, we are at the tail-end of the festive period when we’re positively encouraged to eat all the wrong things, be a bit lazy and less active, which is likely to take you to the top of your weight range. So what is the best thing to do if you want to shift those extra pounds? First, do not go on a low-calorie diet. Start eating like you did before the festive period. “If you go back to normal eating, you will almost certainly lose that weight,” says Dr Jenkinson.
Don’t think in terms of calories. Think about improving the quality of your food, rather than reducing it. Take a healthy lunch to work.
Reduce your insulin levels by considering the glycaemic index of foods. A low-carb choice can reduce the amount of glucose in your bloodstream.
Try to up your omega-3 intake. Dr Jenkinson advocates a full-English-style breakfast, but skip the toast. “It’s important to have a diet that’s high in fat and protein. If you’re a vegetarian, have avocado for breakfast,” he adds.
He is also a fan of eating two good meals a day, and working up an appetite, so that you can really enjoy your evening meal. It’s about lifestyle factors too. Limit your stress levels with good sleep and exercise. “Increased cortisol levels signals to the body that change is coming, potentially famine, so your body will want to put weight on,” he says.
Crucially, avoid unrealistic weight-loss expectations. “By looking after yourself you’re not going to go down to a size 6, but you’re definitely not going to go up to size 14,” says Dr Jenkinson. “You might slowly shift down to size 8 depending on your genetics.”
If you do this then 2020 might be the year that you learn to understand your body. “It might take a year to see real results, but your quality of life will be miles better and you’ll have a much healthier weight,” says Dr Jenkinson. “It’s not about a short-term fix, but a lifelong change.”
How not to diet, yet still lose weight
- Be selective about what you eat
- Try to reduce your insulin level by avoiding sugar and refined carbs like wheat
- Try to normalise omega-3mega-6 ratio by avoiding omega-6 foods: processed foods, fast food, vegetable oil, nuts
- Buy your food from the greengrocers, fishmongers and butchers and prepare your own food where possible
- Eat two to three meals a day and avoid snacking. Enjoy working up a hunger; it’s normal.
- Don’t avoid natural saturated fats
Decrease cortisol levels by...
- Setting your alarm to go to bed. Have eight hours of rest time
- Taking part in an activity that you enjoy that will make you sweat for 20-30 mins at least two to three times a week
- Trying to untangle work and family stresses and taking stock of life
Dr Jenkinson's food rules
Beware of walnuts, use an app and avoid flattening your ‘battery’
At home, use butter and olive oil instead of vegetable oil to fry and bake food.
The olive oil should be bought in a tin or, if in a glass bottle, it should be stored in a dark cupboard as sunlight degrades the healthy antioxidants in the oil.
Do not eat foods that contain, or have been cooked using, vegetable oil. Remember that the cannabinoids in foods containing omega-6 can also be slightly addictive. Avoid:
- Fast foods
- Crisps, microwave popcorn, fried snacks, health bars
- Ready-made cooking sauces
- Margarines and oily spreads
Avoid food containing very high omega-6:
- Grain-fed meats and meat substitutes
- Other foods that you should be aware contain omega-6 in significant levels include cured meats, sausages and tofu.
To optimise your omega-3 to omega-6 ratio, follow some simple rules. Eat lots of greens, and eat lots of meat and fish that have eaten their greens; you can also include dairy products (and, yes, butter is OK). Cut out vegetable oil, seeds (including grains) and processed foods. Because the good foods tend to be fresh for only a short period of time, you will have to shop regularly and you will have to cook.
A special mention should be made of nuts and dried seeds, and foods made up predominantly of nuts and seeds, sold as “healthy” snack bars, which are very high in omega-6. For example, walnuts are often championed as a great source of omega-3 – but their large quantities of healthy omega-3 are rendered useless by the amount of omega-6 they also contain.
Measuring your daily glycaemic load
Before you start trying to reduce your glycaemic load (GL), you should measure your current level. You can calculate the amount of carbohydrates you consume by using an app on your smartphone such as MyFitnessPal.
You may need to invest in kitchen scales (if you haven’t already) to get an idea of the size of your portions by weight. The app can then calculate the GL of each individual food and add up the daily total.
150, 100, 80 or 60 grams?
Most people who are not dieting will consume in excess of 300 grams of carbohydrates per day: that is a total glycaemic load of more than 300. I think that a good starting target for your glycaemic load should be 150g per day. This should be easily achievable, especially as you are already avoiding any significant carbs for your breakfast. Once you become more aware of the high-carb foods in your diet, the next step should be to get your daily GL down to 100. Do not rush this. It is much better to make slow, planned changes over weeks rather than days.
Your ultimate target could be as low as 80, but this will depend on how your body is responding to the changes and how you are feeling, whether you are able to cope easily with these changes and are enjoying their health benefits. Remember, if any part of the programme is not enjoyable it is much less likely that it will become part of your daily routine, and therefore part of you.
Don’t go keto
The aim is to lower your insulin levels by reducing your total carbohydrate intake. But we do not want your carb intake to go so low that your liver runs out of reserves and you become ketogenic. Sometimes this can happen if you are simultaneously exercising and cutting your daily carb intake.
If you feel particularly weak, or experience symptoms of ketosis such as headache, nausea or vomiting, then it might be that you have exhausted your liver’s reserves of carbohydrate (your “battery” is flat). You should be aware that exercise can drain your liver of carbs and tip you into ketosis if you are not replacing them. So here is the good news: you need to replace those carbs that you burn during exercise – you can add them to your daily allowance.
Why We Eat (Too Much): The New Science of Appetite by Dr Andrew Jenkinson (Penguin, £16.99) is available from books.telegraph.co.uk
Why everything we know about weight gain and dieting is wrong
For nearly two decades, bariatric surgeon Dr Andrew Jenkinson has treated thousands of people with obesity. In the second part of our exclusive serialisation of his new book, Why We Eat (Too Much), he debunks the myths around dieting and weight-loss.
Our old-fashioned understanding of obesity is slowly being challenged. Many scientists are realising that it is not the quantity of calories that are available in the food supply to a population that will affect obesity levels: it is the quality of the food available that causes obesity. Natural foods do not make populations fat. If a grain, oil and sugar based diet is fed to any population of people high levels of obesity occur.
Contrary to popular belief, our metabolism isn’t under our control and can vary dramatically depending on how much we eat. In those who diet a lot, their weight set-point – the level of energy (fat) storage that our brain calculates is necessary for our survival – shifts. The more diets you’ve been on, the higher your weight set-point and the slower your metabolism, because your body wants to protect you.
Why (most) diets don’t work
Low calorie diets
Very low calorie diets (600–1,200kcal/day) like LighterLife or SlimFast generally use meal-replacement shakes and soups and by definition are not sustainable if you want to have a good quality of life (i.e. be able to eat). Low-calorie diets cause changes in our metabolism. In the long run they raise your set-point, meaning that when you come off the diet you will regain all your lost weight and then some more until your new weight set-point is reached.
Low carb diets
The Atkins, Paleo and Dukan diets are based on low-carb eating. Once carbohydrate intake is reduced to under 20 grams per day, a process called ketogenesis occurs. There are many celebrity advocates of ketogenic dieting, such as Kim Kardashian. It is an effective way of reducing weight but it has very unpleasant side effects, from a pounding headache to weakness, constipation and flu-like symptoms. The aim of the ketogenic diet is to starve your body of carbohydrates so it has to use up its own stores.
By not taking in any food that can be broken down into glucose, you are forcing your body to start using the reserve that is stored in the liver. As with most diets, if you lost a lot of weight dieting this way, and then reverted to eating more normally again, you would regain all of that lost weight . . . and more.
Popular examples of intermittent fasting are the 5:2 diet and the 16/8 diet. The 5:2 diet involves eating normally for five days, and limiting calorie intake to 500 or 600kcal for two days. The 16/8 diet advocates eating during an eight-hour window in the day. Both diets advise avoiding processed foods.
Unlike many other types of diets, intermittent fasting, just like low-carb dieting, remains popular - which means that it probably does work for some people. How does fasting work? By decreasing the opportunities for eating, and at the same time by avoiding processed foods, both the insulin profile and the omega ratio of the dieter will be improved and therefore the weight set-point will be reduced.
Vegetarian and Vegan Diets
Many vegans or vegetarians eat out of concern for the environment and animal welfare, but are these diets helpful for weight loss? Two of the main causes of an elevated set-point (and therefore weight gain) are unnaturally high insulin profiles and a relative deficiency of omega-3 compared to omega-6 essential fatty acids. Most vegetarians and vegans will eschew many types of processed foods because they contain animal products. This has a positive effect on both the amount of sugar and the amount of omega-6 oils they consume. However, frying foods in vegetable oils and consuming nuts and seeds (all high in omega-6) will have a detrimental effect on their omega profile, particularly as fish (a valuable source of omega 3) is excluded from their diet.
They also may consume a lot of bread, pasta and rice, which has a detrimental effect on their insulin profiles and weight. However, I find most vegans and vegetarians are aware of the quality of their food, more inclined to prepare their own meals and more likely to avoid processed foods. If they can avoid taking in too much sugar or refined carbohydrates, their set-point (and weight) will fall.
How to curb cravings
Many people report fewer cravings when they start to eat well. However, there are times when certain foods seem to be calling us! The chocolate in the fridge says, ‘you deserve a treat, you have had a hard day.’
It is important not to underestimate the intensity of cravings. Many of my patients say they feel edgy, agitated and restless while experiencing a craving and most say it becomes difficult to reason with themselves. So how can you manage cravings?
Get moving – there is a lot of physical agitation associated with cravings and moving can ‘burn up’ this extra energy. Some of my clients dance or march on the spot. It is not simply about distraction; it is about directing this extra energy.
Surf the urge – what goes up, must come down! People often believe that an urge or craving will keep building. However, when we allow ourselves to observe an urge we often notice it builds in intensity and then disappears.
And breathe - cravings arise from a high-energy state, which we can lower by remembering to breathe. An audio download of a three-minute breathing exercise can be found at https://franticworld.com
We need to re-think our omega fats
Ideally, and throughout history, the ratio of omega-3 to omega-6 within our bodies would have been between 1:1 and 1:4 (i.e. four times more omega-6 than omega-3). If we go back to hunter/gatherer times, when food was fresh and not based on grains or vegetable oils, we would see this range.
People living in remote areas of the world today, who consume natural home-grown foods, will have these levels as well. But if you consume a Western diet, many omega-3s have been removed and large amounts of omega-6 have been added to foods that have been processed.
So, the omega-3 to omega-6 ratio rises to a staggering 1:50 in some Westernised cities. The more omega-6 in the cell wall, the more that the appetite and weight regulating system will be ratcheted towards weight gain. An increase in the omega-6 to omega-3 ratio has been in implicated in: Alzheimer’s disease, dementia, anxiety mood disorders and suicide.
To optimise your omega-3 to omega-6 ratio, follow some simple rules. Eat lots of greens, and eat lots of meat and fish that have eaten their greens - many farms feed their livestock an unnatural grain-based diet containing omega-6, in order to make them grow bigger faster (it works for animals as well as humans) so you will have to source grass fed meat very carefully.
This goes for fish too - farmed salmon that has been fed grain will have a much poorer omega-3; omega-6 profile than line-caught fish. You can also include dairy products, including butter. Cut out vegetable oil, seeds (including grains) and processed foods. Because the good foods tend to be fresh for only a short period of time, you will have to shop regularly and you will have to cook.
What alcohol does to your weight set point
We know that alcohol can cause many serious illnesses, from heart disease and cancer, but how much does our alcohol consumption contribute to obesity? When we count the calories, it looks bleak. For UK adults, the average weekly alcoholic calorie intake is over 1,800kcal. But my book is all about not counting calories and instead questioning how different factors affect us metabolically. So, for now, let’s push away guilty thoughts about how many calories alcohol contains and think about how it influences our weight set-point.
Interestingly, alcohol can improve insulin’s function, making it more efficient. But the side effect of this is when we drink alcohol it can lead to lower levels of blood sugar. The brain senses this and tells us to eat – producing the late-night craving for a kebab or morning fry-up. Alcohol, because of its effect on blood-sugar levels (and cortisol), heightens our appetite and makes us eat more. If this extra food is high in sugar, wheat or vegetable oils then it raises our weight set-point.
In addition, moderate or heavy drinkers have higher cortisol levels, causing fat to be distributed to the abdomen. By cutting down your alcohol intake significantly (or quitting) your weight set-point and weight will fall. If you are an occasional or light drinker, and if you make good food choices when drinking, then it is unlikely that it is having a significant effect on your weight set-point.
Last edited by Demi : Sun, Jan-05-20 at 12:01.