The Expert:
Dr Giles Yeo is a geneticist with two decades’ experience studying obesity, based at the University of Cambridge. He is the author of Why Calories Don’t Count and Gene Eating.
MH: A reduced-calorie diet is generally considered the key to weight loss. But you’ve argued that most diets ultimately fail. Why is this?
GY: In a sense, the majority of diets do work. They get people to eat less, which means they lose weight. The problem is keeping the weight off. The way we’re set up evolutionarily is that the brain hates it when you lose weight; it considers it a reduction in your chances of survival. So, your brain will drop your metabolism slightly and it will make you hungrier. It’s worse when you’re on extreme diets. The weight comes back on even quicker.
What’s the alternative?
The only way to lose weight is to change the way you eat forever. You’ve got to put together a lifestyle strategy for keeping it off. It will always be difficult, and anyone who tries to tell you it’s easy is lying.
Why can’t calorie-counting be a part of that lifestyle strategy?
Clearly calories do count to some degree; they reflect the energy content of a food. Let me tell you where they’re useful. If I need to reduce my intake, I can halve my portion of chips, from 500 calories to 250 calories. That’s legitimate, because it’s the same type of food. Calorie counts are also useful at point of purchase. If you’re at Costa and you see a muffin has 400 calories, it influences your chances of buying that item.
What doesn’t make sense is blindly counting them, because it makes a difference whether you’re eating 100 calories of celery versus 100 calories of sugar. People say all calories are equal.
Are they not? Nutritional benefits aside…
No. We process different foods very differently. The number on the packet does not equal the number of calories you end up using. What’s not reflected is the amount of energy it takes you to “get at” the calories. Something like fat doesn’t cost a lot to break down. It’s 97% calorically available. Carbohydrates? It depends whether we’re talking about wholemeal bread or sugar. Wholemeal bread is 92-95% available, sugar is 95-97%. The big difference lies in protein. For every 100 calories of protein we only absorb 70 calories.
How much of a difference does that make?
It doesn’t make a big difference from meal to meal. But over every single meal of your life, it will. If you look at foods which aren’t high in quality, particularly ultra-processed foods, they tend to be low in protein and fibre, both of which are less calorically available. The amount of protein and fibre in foods is an easy marker of quality. It’ll make you feel fuller, too. If you are able to harness your biology to make yourself feel naturally fuller, then at least you have a fighting chance.
In one study, published in Food & Nutrition Research, two groups were given sandwiches with identical calorie counts: one made with whole foods, the other heavily processed. The former required 47% more energy to digest.
What would you say to someone who wants to lose weight in a way that’s sustainable and not painful?
I can’t claim that it won’t be difficult!
Then let’s talk about minimizing pain. What advice would you give?
Concern yourself with the quality of the food you’re eating. We should be better at this – as policy makers, as scientists and as people trying to make food choices. Looking for ways to improve the quality of your diet will improve your health, and if you focus on your health, your weight will sort of take care of itself.
Focusing on the quality of your food – limiting sugar and processed foods, and eating more whole foods – has been shown to lead to greater weight loss than focusing on calories and portion sizes, reports a Stanford University study.
A lot of calorie-counters whose primary goal is weight loss would find that contentious…
Start by asking why you’re trying to lose weight. And be honest. There’s going to be a reason. If you want to lose weight to look good, then what’s your definition of “good”? I want to look like Brad Pitt, but I don’t. You might not be totally happy with how you look, but are you healthy? Are you able to lift your child up? Are you able to go out and cycle? Are you eating high-quality food? If the answer is yes and you can maintain your weight, then perhaps that’s what you should do. There’s an element of getting people to be realistic.
Do you believe in the concept of a “set point” weight?
I usually refer to a set range. Say I lose half a stone. Keeping that off will require effort. But if I stay where I am, there’s almost no effort. My current habits – I exercise, I do my commute, I eat what I want on weekends – mean I’m not gaining weight. Your set range is where you’re stable.
If you’re an MMA fighter or a model, that’s a different thing. But those careers are short. For most of us, what we want is to be able to walk up the stairs or go for a run without feeling out of breath. Look, at lot of people do need to lose weight, I’m not saying they don’t. But a lot of people just need to be healthier.
You talk a lot about the importance of combatting weight stigma. Does that feel like a hard line to walk, given your job is to study obesity?
As mature human beings, we should be able to hold two thoughts in our heads at once. Obesity is a problem. But then there’s blaming people who are suffering from that problem – people conflate the two. Undoubtedly, the prevailing view is that our bodyweight is a choice. We only know ourselves. If I stop eating a pizza after two slices because I’m no longer hungry, I might look at a person who had four slices and think, “Why did he need four?” But it’s the equivalent of someone stopping me at one slice and telling me I can’t have a second. Our thermostats are set in different places, biologically. Some people think they have more willpower, but we are just looking at ourselves and projecting onto other people.
According to Dr Yeo’s own research, some people are genetically 5% less likely to be able to say “no” to excess food, which makes choosing satiating foods – those high in fibre and protein – even more crucial.
Clearly this topic is nuanced. And yet your own eating guidelines are very simple: enough protein, more fibre, less sugar and less meat.
It sounds boring, but it’s as close as I’m going to get to a plan. And it’s not a diet – it’s just eating sensibly.
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