Tuesday, July 20, 2010

What is in control of your appetite 2

In an earlier blog I mentioned that there is an internal drive to eat, grow and reproduce and this seems to over-ride the decision to eat well for a long life. We tend to over-eat to contend with famines although most of us haven’t experienced a food shortage since television.

Protein is life

We know how much protein is needed for growth and maintenance yet nearly all of us eat more than we need and actively seek high protein foods. In the US 97%, and in Australia over 90%, of the population eat more protein than needed (around 0.8g/kg day). As countries “develop” they tend towards an increase in protein intake. We love big steaks, seafood platters and, of course, triple bacon, double cheese, egg, thin slice of tomato for colour, megaproteinburgers.

A theory is that a high protein diet brings forward the onset of puberty and so extending the period of fertility. In affluent western societies the onset of women’s menarche is 11 years, while in rural China it is 17 years.

Protein is death

The bad news is that the desire to track down protein is linked to a shorter life. A moderate protein, calorie-restricted diet increases the lifespan of laboratory animals by around 20% compared to high protein diets. On the other hand (and I’m so glad we have two hands because there are so many on-the-other-hand situations in life) high protein foods are more satisfying than high carbohydrate foods so people are more likely to stop eating before they get too podgy. In theory.

Health campaigns ignore genes

We love food. Nature designed us that way. We love calorie-dense foods with plenty of protein and fat (hamburgers), and protein, fat and sugar (chocolate). The authors of this paper argue that our in-built tendencies are usually ignored in health campaigns and scientific study. For example, a campaign urging us to eat low calorie fruit and vegetables doesn’t make sense to our genetic desire for calorie-dense foods.

What does it all mean?

We were never designed for a long life, just a life long enough to get our children to reproductive age, so four decades is about all that is expected. And millions eat like they are happy with four decades before they clutch their chest and hit the floor. Dietary advice today runs counter to our natural instincts to eat foods that give us both pleasure and calories/kilojoules to reach a reproductive age.

Living to the age of 80 years is a relatively new experience for humans. Before the industrial revolution, 40-50 years was about all you could expect unless you were gentry. Go back 1000 years and you were looking at 30-35 years to be labeled “old”. For those us who are aiming to clock up eight or ten decades then eat like you want to live to 100, and live like you might die tomorrow. Just know, it won’t be easy.

Reference: Appetite. 2010; 54: 442-449

Banana vending machine

I read with interest that Japan launched its very first banana vending machine on June 23rd in Tokyo’s Shibuya station. Fruit in a vending machine is a novel idea and should be applauded. I just hope that after you pay your $US1.50 for a single banana ($US4.50 for a bunch) that it gets treated gently by the machine and doesn’t drop the equivalent of six banana stories from the top of the machine.

Dole, the biggest fresh produce company in the world, has provided the machine. When I squint hard enough, I’m pretty certain that Captain Banana, if that’s his name, has a banana mo.

Monday, July 5, 2010

What is in control of your appetite?

With democracy and affluence comes overweight, poor food choices and laziness. OK, not laziness, just the decision to remain on one’s bottom for hours and hours. Why don’t people in well-off countries eat more healthy and get out and boogie? Find a solution to that and you can write your own ticket.

Genes meet environment

A bunch of European scientists believe that part of the problem is that some nutrition decisions are genetically determined and very difficult to change. It seems that the environment doesn’t change your genes, but it does determine which genes are turned on and off.

Having abundant food around increases the individual limit for food to be satisfying. One paper showed that changing to a healthier diet for a few weeks modulated the response to over 500 genes. In other words, gene expression returned to normal. Sadly, the environment tends to over-ride this for many as we are surrounded with eat-me, buy-me cues, returning gene expression to over-eating.

Time of the season

Animals that experience seasonal or daily variation in food availability (think of hibernating or hunting animals) tend to eat more than is necessary when they find food. They store the excess food as body fat, which is then used during times of food shortage. When these animals experience long-term abundance they over-eat. Humans are one of these animals. In affluent democracies not only are half of the humans overweight, half of the cats and dogs are too.

It’s not just humans that prefer processed and cooked food, the great apes are a big fan as well. Many other wild animals prefer cooked food to raw. Choosing foods that are rich in kilojoules means that an animal will grow faster, reach reproductive age quicker, protecting the survival of the species. The authors argue that this hard-wiring to eat, grow and reproduce is one reason we choose cooked and processed high kilojoule/calorie foods over minimally processed foods.

Gene defect

There are the unfortunate who have a specific genetic defect that drives them to eat too much, such as Prader-Willi syndrome. I used to look after kids with this syndrome when I worked at the Children’s Hospital in Sydney deep in the last century. By default, I became the Australian expert on PWS and spoke at conferences. It’s tough for parents when you have to lock all food cupboards and the fridge because your child’s appetite has no off switch. Ever.

What does it all mean?

Now, I can’t say I fully understood this paper, but the jist seems to be that we are similar to other animals in that we are genetically geared towards over-eating as that makes us more likely to survive famines, live to maturity and reproduce. Go to the paper if “epigenetic mechanism of methyl–cystine bonding” in gene expression sparkles your mind.

It also means, and this bit is worrying me, that if you have children and have now brought them up to a reproductive age, then you are no longer required by nature. Watch your back.

Reference: Appetite. 2010; 54: 442-449

What does the M in M&Ms stand for?

I answered this question for the local paper recently. Even most people at Mars don't know the answer to this. They, and others, mistakenly presume that both Ms stands for Mars, yet they are called M and Ms for a reason.

M&Ms were first produced in 1941 from an idea by Forrest Mars when he saw soldiers in the Spanish Civil War eating sugar-coated chocolate. The sugar coating protected the chocolate from melting and this inspired M&Ms, a chocolate that "melts in your mouth, not in your hand". The first M in M&Ms is for Forrest Mars, the inventor of M&Ms.

William Murrie was president of the Hershey Chocolate Company. His son, R. Bruce Murrie, became a partner with Forrest Mars in his project and he helped Forrest acquire and modify Hershey plant machinery to be able to produce M&Ms. The two of them initially set up the company M&M Ltd.

The second M in M&Ms stands for R. Bruce Murrie. Some sources say the second M stands for his father, William Murrie, as he had given his blessing to the partnership.

Forrest Mars eventually bumped R. Bruce Murrie out of the partnership, hence people at Mars say the Ms stand for Mars and Mars, while historians at Hershey say the Ms stand for Murrie, a well-known Hershey family ... and Mars.

Source: The Emperors of Chocolate by JG Brenner (Broadway Books, New York 1999)