The message of the study was that exercise activity is easily compensated for – the body will fight to maintain its weight set-point whether that means metabolic hyper-efficiency in active people who don’t over-eat, or metabolic inefficiency in those who are sedentary and over-eat: the crux is the set-point.
The Stressed, ‘Hypertensive’, Overweight New Yorker
The research study did confirm one expected difference between the two populations of people studied – their size. When comparing the slim Hadza to the fat New Yorker it is not a calculation of the total calories taken in compared to the total calories expended in exercise – this is far too simplistic. No, the New Yorker has been exposed to environmental signals that have raised their set-point. Yes, we know the restaurants in New York are some of the best in the world, but it is the quality of the food and not the total calories consumed that determines the set-point. The New Yorker would have been exposed to large amounts of processed and fast foods – leading to a major derangement of the omega-3 to omega-6 cell membrane ratio, as well as to chronically high insulin requirements. Add to this the stresses of city life, and maybe the disturbance in melatonin levels due to poor day/night differentiation, and you have multiple factors elevating the set-point higher and higher.
How Does Exercise Work?
So, we have a dilemma. The active Hadza tribe didn’t expend more energy than the sedentary New Yorkers. If regular exercise is compensated for by metabolic adaptation, if it makes us more efficient at resting and we therefore don’t burn off more calories, how does it work?
I think that we can safely say that exercise does produce weight loss (otherwise gyms would not be so popular). It’s just that the weight is not lost by the simple energy in/energy out equation that most people imagine. It is lost because exercise itself causes our weight set-point to decrease. Only once this has happened will the body let that energy go (probably in the gym) and the weight will come down.
Regular strenuous exercise will cause two major changes that affect our weight set-point:
Decreased cortisol (the stress hormone)
Improved insulin sensitivity (leading to lower insulin levels).
We can summarize as follows:
Exercise ➞ lower cortisol ➞ lower set-point
Exercise ➞ improved insulin sensitivity ➞ lower insulin ➞ lower set-point
The lower set-point then directs the body to lose weight.
The importance of exercise is not therefore about the calories expended, it is about how the activity improves your metabolic health by decreasing your cortisol levels and improving insulin sensitivity. Exercise can have a bigger impact on weight if you can find the time in your schedule to train like an athlete. If you perform intense activity for two hours a day, expending 1,000kcal/day, most days a week, then this is something that metabolically the body cannot ignore. But for most people this is not something they can fit into their daily routine.
One of the other major benefits of exercise is that it produces a significant increase in your ‘good cholesterol’, HDL. This trumps all other types of bad cholesterol and will significantly reduce your risk of heart disease.
Activity Rules
Choose an activity that you enjoy
Choose an activity that is practical for you
Exercise two or three times per week for a minimum of twenty minutes
Exercise enough to sweat (this is important for it to work)
Avoid endurance exercise.
It’s important for the activity to be one you really enjoy – not everyone likes going to the gym. Personally I am slightly intimidated by the muscular guys sashaying naked around the changing room, sniggering at my (not so muscular) body, and I imagine that many other people also feel uncomfortable in that environment. Find an activity you will look forward to and really enjoy, one that can enrich your life. Perhaps swimming, yoga, tennis or squash? If time is an issue, and you used to like cycling, then cycle to work and back occasionally. If you prefer team sports, there are football, netball or hockey. You might just like to walk, and a brisk walk with a bit of an incline can be good and enjoyable outdoor exercise; or, like me, you might want to go for a jog (or even a walk and a jog). If you are not very good at sport, then look out for lessons or a club and take up something new. You may choose to get a rowing machine or treadmill in your own home and watch TV or listen to music when you exercise. The main point is it has to be enjoyable for you; otherwise you will stop doing it after a while. Also remember, exercise isn’t about counting calories off – we should be exercising to improve our metabolic health, to lower our insulin and cortisol levels and also to improve muscle tone. Muscle health, as we are about to learn, is essential for our weight regulation.
Keep Your Muscles Strong
In addition to improving your metabolic health, exercise contributes to muscle health. There are some societies in the world, particularly the Middle East, where extreme sedentary behaviour, especially amongst women, is almost expected – it is the cultural norm. When you are not expected to perform any household chores, and it is unladylike to walk long distances (unless in the shopping mall), then over time your muscle mass will shrink and you will develop a condition called sarcopenia (meaning small, withered muscles). As we found out in chapter 3, by means of metabolic adaptation in our muscles, we literally burn off the excess calories consumed (this is known as thermogenesis). Therefore, when muscle mass shrinks, our ability to burn off excess calories is compromised. If you combine small muscle mass with larger quantities of calories (for instance, by eating sugary snacks), only one thing will follow: significant and rapid weight gain. This is why Middle Eastern women now have staggering obesity rates nearing 50 per cent.
The key message for you to keep in mind is: maintain muscle strength and muscle mass. Keep your essential muscle organ healthy. If you are a ‘couch potato’ in the evening, don’t worry, as long as you do some short, intense, muscular activity before your down-time. If you don’t have time for, or don’t like, the gym, try something like the 7-Minute Workout app. It will ensure all-round muscle health – and allow you some me-time.
STEP 5 – REDUCE YOUR INSULIN
We have now arrived at the final step in optimizing your weight. If you have made it to this point, congratulations! I hope that you are enjoying your new, much healthier life. So far you have given up sugar and highly refined carbohydrates, improved your sleep, optimized your cellular health and are performing an exercise that you enjoy. In the final part of the programme we aim to reduce your carbohydrate intake slightly more, and by doing so reduce your insulin requirement – as we know by now, this will reduce your weight set-point.
There are different varieties of low-carb diets from the extremes of ketogenic dieting (discussed in chapter 12) to the more moderate ‘low GI diet’. We are going to go for something in between – something that will be effective, but also can be sustained as part of a normal eating routine.
Usain Bolt vs Mo Farah
You have probably heard the term glycaemic index (GI). It is used to describe the speed at which a food releases its carbohydrate energy into the bloodstream. The higher the GI of a food, the faster it releases its sugar energy. It is used to identify foods that will give you that sudden insulin spike I described in chapter 10 and is the basis for the low-GI diet. In this diet, participants are asked to avoid foods that have a high glycaemic index and to choose only foods that release their glucose slowly. Because the diet normalizes blood sugar fluctuations, it is particularly useful for diabetics on insulin. The type of GI foods that you are encouraged to eat while on the low-GI diet would include grapefruit (GI of 25), cherries (22), apples (28) and sweet potatoes (40).
The types of foods that you are told to avoid in the low GI diet are white potatoes (85), white bread (70), watermelon (72) and carrots (47).
But the glycaemic index does not tell the whole story about the food that you are eating.
Consider this question. Wh
o would win in a race between Usain Bolt and Mo Farah? You can imagine them lining up against each other under the floodlights in the Olympic stadium in London. The starter is ready to fire his pistol. Many people would probably not think the question through and would automatically say, ‘Usain, of course’. But they are assuming the race is over a short distance. They are answering the question: ‘Who is the fastest?’ But if after the starting pistol has been fired, and the lightning-fast Bolt sprints into an extremely healthy early lead, the finish line does not appear … then the runner with more stamina will have a chance. As the muscular bulk of Usain starts to cramp up, you can imagine Mo Farah gliding past him – and the MoBot will win.
The Glycaemic Load
In just the same way that runners should not be defined only by their speed, so a food should not be defined only by its glycaemic index. It is not just the speed at which the food releases glucose into the bloodstream that is important, but the total amount of glucose that is released. This is where I think the glycaemic load becomes much more important – in predicting total insulin levels – than the glycaemic index.
The glycaemic load defines the full effect that a portion of food will have on your blood glucose level (not just the speed). One unit of glycaemic load has the same effect as consuming one gram of glucose (4kcal). It is influenced by the portion of the food that is eaten, so doubling a portion of food will double its glycaemic load. For example, if we adhere to the low-glycaemic-index diet principle we will see that watermelon is a fast releaser of glucose. It just sprints into your bloodstream with a GI time of 72, whereas a low-fat yogurt is much slower (GI of 33). But the food equivalent of the MoBot has much more energy stored within it. The yogurt’s glycaemic load (GL) is 16 per pot, compared with a slice of watermelon that has a GL of only 8, half the amount. So in the long run a pot of yogurt increases insulin by double the amount compared to a cup of watermelon, despite watermelon having a much higher glycaemic index.
Here are some examples of the glycaemic loads of common foods:
Staple Carbs Fruit and Vegetables Meat and Dairy
White potato 29 Orange 4 Beef 0
Sweet potato 20 Apple 5 Chicken 0
White rice 24 Banana 10 Eggs 0
Wild rice 16 Grapes 9 Milk 9
White bread 16 Green beans 4 Cheese 1
Brown bread 10 Tomato 2 Pulses
Rice pasta 21 Spinach 2 Beans 12
Rice noodles 21 Carrots 2 Chickpeas 20
Table 16.1 The glycaemic load of common foods Note: Portion sizes: potato (large size), rice, pasta, noodles (150g serving), bread (2 slices), fruit (1 item), grapes (1 handful), vegetables (1 medium cupful), milk (250ml), cheese (half a cup, diced), pulses (half a can, 200g).
Source: USDA National Nutrient Database for Standard Reference, April 2018.
There is also an extensive table of the glycaemic loads of different foods in Appendix 2. You will see that meat, fish, eggs and cheese have a GL of zero and that most fruits and vegetables have a low GL. Our blood glucose mainly comes from our staple carbohydrate foods (potatoes, pasta, rice and noodles). I do not want you to give these staple foods up and start to crave them, or even to develop the unpleasant side effects of the ketogenic diet – but I think that it will be beneficial for your insulin profile and therefore your weight set-point (and ultimately your weight) if you slowly try to reduce the overall amount of glucose entering your bloodstream every day. By reducing your total glycaemic load you will be able to do this. As I have explained throughout this book, it is not the total number of calories that you consume that matters, it is the quality of the food that is important. When you cut down on your portion size of staple carbohydrates, you should compensate by topping up on low GL vegetables and high-protein and high-fat foods.
Measuring Your Daily Glycaemic Load
Before you start trying to reduce your glycaemic load, you should measure your current level. You can calculate the amount of carbohydrates that you consume every day 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 over 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.
The 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 of our plan 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 keto flu 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. Most moderate exercise, such as jogging, working out in the gym or playing football or tennis, will burn 250–350kcal per half-hour session. This energy is taken from your liver: 300kcal translates to 75 grams of carbs, which would be the equivalent of an extra-large baked potato, a portion of rice and a banana – all on top of your daily GL target. Seems OK, maybe worth the effort … and certainly better than topping up with a single Snickers bar (270kcal).
Finishing Line
I hope that you have enjoyed the steps of this programme and that you are finally winning the diet war – once and for all. The changes to the working of your body that each of these steps makes can be variable, and can take weeks, even months. But if you persist with the way of eating and living set out in this book those changes will soon become ingrained into your body. Eventually your body will reflect the way you live. Your weight set-point will be permanently lower, meaning easy, seamless weight regulation and a long-term improvement to your metabolic health.
EPILOGUE
Why Do We Eat Too Much?
When my very helpful editor at Penguin suggested we name this book Why We Eat (Too Much), I had to sit down and think it through. A more appropriate name for the book would have been something like ‘Why Do Some of Us Store Too Much Energy (and Others Don’t)’, but this was clearly too long-winded and wasn’t going to catch the eye of potential readers, or get the messages of the book out there into the public domain (the main reason for writing it in the first place).
Before reading these pages, many people attempting to answer this question would have replied, ‘Because we are greedy’, or ‘Because food just tastes too good these days’. But as we have learned in this book, it’s a lot more complicated than that.
In truth, as we saw in chapter 1, most of us eat too much nowadays, a lot more (500kcal/day) than we did thirty years ago. But we also learned that despite eating more we also metabolize more. We are able to adapt to over-eating and burn off most of the excess energy effortlessly. Therefore weight gain doesn’t happen as dramatically as we would expect. Remember the analogy with a delivery of logs for your fire i
n chapter 1? If more are delivered, you tend to burn more. If you eat more, you metabolize more. But that doesn’t explain why many of us seem to be storing some of those extra logs for another day.
The Three Houses
Imagine three identical houses next to each other in the countryside. Each house is heated by a log fire and each house has a storage shed for logs outside the front door. All the houses receive an ample delivery of wood every day, more than enough to keep warm.
The first house has minimal wood in its storage shed and yet there is a constant plume of smoke from its chimney, and some of the windows are open to let heat out.
The second house’s storage shed is almost full of logs. Its plume of smoke is less than house one’s, and its windows are closed. The owner is clearly being frugal with his wood until he has more logs delivered and the shed is full.
In the third house the wood shed is damaged. This happened when it was over-filled. But there is a mountain of wood piled up by the side of the house. Despite this, the owner appears to have doubled his delivery order.
So three identical houses, but why are there three very different stores of logs?
The first house sits next to a forest. Its owner knows that there will never be a shortage of wood. There is no need to store much and in fact excess logs are regularly burned.
The owner of the second house is more cautious. His delivery man went on strike last year, leaving him with dwindling stocks of logs and a cold house. In addition, he recently heard on the radio that an icy spell of weather is approaching. Understandably he wants his shed to be full to the brim with logs.
Why We Eat (Too Much) Page 30