Brain damage caused by fatty food might be one reason why people who habitually over-eat find it so hard to lose weight, scientists have said.
New research suggests that saturated fat can destroy neurons in a part of the brain that controls energy balance and appetite.
Researchers found changes to vital genes and proteins in the brains of mice fed a high fat diet.
The effects in the hypothalamus - the brain's energy centre - indicated the kind of damage normally caused by inflammation and blood clot strokes.
Lead scientist Lynda Williams, from the University of Aberdeen Rowett Institute, said: "These changes may underlie the breakdown of energy centres in the brain and may explain why its so difficult for obese people to maintain weight loss from dieting.
We're firm believers of the "everything in moderation" principle, but it's all too easy to stretch the limits of what counts as moderation. There's a big difference between having a few fries at your favorite diner, pub or fast-food joint and ordering the largest size on the menu. Take McDonald's for example. A medium-sized order will set you back 380 calories and 19 grams of fat. But switch to a kids' order and you'll save big: This smaller size has only 100 calories and five grams of fat. Flickr photo by Calgary Reviews
When it comes to fried foods, the less you eat, the better, says Gayl Canfield, Ph. D., R.D., nutrition director at the Pritikin Longevity Center. You'll eat less if you split the order with someone else. "Order it, and share it, along with other, healthier foods," she recommends. Flickr photo by Ian Sane
A number of chain restaurants, like Five Guys, advertise the fact that they use peanut oil in their cooking, which results in at least a slightly healthier batch of fries. Peanut oil is great for frying because of its high smoke point and neutral taste, according to Serious Eats, but it also has less saturated fat than lard, beef fat or duck fat, says Canfield, all of which are used on French fries. Plus, peanut oil also boasts heart-healthy poly- and monounsaturated fats. If your favorite restaurant doesn't openly disclose what kind of oil they use, ask your server. Flickr photo by Steve Snodgrass
Shoestring, curly, waffle, wedges -- there is a style of French fry for just about everyone, but is there a healthiest cut? The thicker the better, Canfield says. A smaller fry packs less potato and more unhealthy fried surface area, she says.
Eating your fries slowly may help you eat just a few, Prevention.com recommends. Not gobbling up your food is a healthy idea in general, as it allows time for the brain to register when you're feeling full before you have time to wolf down more calories. Savoring each bite may help you take fewer bites all together. Flickr photo by Steve Snodgrass
If you're going to be "celebrating" in the comfort of your own kitchen, you have a few more options to get healthy -- and creative. Baking or roasting potatoes drastically cuts back on the amount of oil absorbed into the spud, says Canfield. Cut them into thick wedges, sprinkle on your favorite herbs (she loves dill!) and pop them in the oven until they're golden-brown. Flickr photo by Christian Cable
Potatoes get a bad rap, but they actually made our list of 50 of the healthiest foods thanks to their mix of complex carbs, vitamins and fiber. You've probably already tried sweet potato fries, which may have a healthy leg up on the white stuff, thanks to beta carotene, but "it's what we do to them that makes them unhealthy," says Canfield. An order of deep-friend sweets, that means, might not actually be a whole lot better than the regular kind. That said, there are a number of other superfoods that make for healthier sides -- and are even better baked or roasted. There is a seemingly endless number of recipes for healthy French fry alternatives made with everything from zucchini to parsnip to kohlrabi. "I've seen squash fries, green beans, but it's all the same concept," says Canfield. "You could oven roast them and have a much better outcome calorically and nutrition-wise." Flickr photo by Will Folsom
"Another thing you can do especially with vegetables is put them on the grill," says Canfield. "Make big wedges of potato and zucchini and onion and grill in a grill basket and it's really yummy," she says. That technique may even give you a little of the crunch you're looking for. Flickr photo by woodleywonderworks
"Our results indicate that a high fat diet can damage the areas of the brain that control energy balance and perpetuate the development of obesity.
"High fat and high sugar foods are energy dense foods which are highly palatable and they are very easy to over-eat. Our findings may also explain why some overweight people find it difficult to diet and why weight loss after dieting is so difficult to maintain.
"We now plan to carry out further studies that will look at whether these effects are reversible."
She pointed out that brain scan studies in the US had shown signs of hypothalamus damage in obese individuals, suggesting that the effects seen in mice may also occur in humans.
The hypothalamus is a small area at the base of the brain that contains neurons which govern energy expenditure and appetite.
"This control breaks down in obesity - the system appears not to work - and we don't really know why this happens," said Dr Williams, speaking at the British Science Festival at the University of Aberdeen.
"In our study we found that genes and proteins change in response to a high fat diet and that these changes are normally associated with damage to the brain, indicating that damage had occurred in the hypothalamus in mice that ate a diet high in saturated fat."
The changes happened quickly, she said. It took three days for proteins to be affected and a week for visible signs of disruption to genes to appear.
Dr Williams acknowledged the effects might be exaggerated in mice whose diet was drastically altered so they obtained 60% of their energy from saturated fat.
Could these foods cause brain damage?
When health experts say to eat fish a couple of times a week, they don't mean any and all fish. Not only are certain types healthier for you (and the environment), but how the fish is prepared also makes a big difference, with fried dishes of course being the worst offenders. No one expects fish and chips to be a healthy choice, but Applebee's New England Fish & Chips has a jaw-dropping 138 grams of fat, about the same as one and a half sticks of butter and more than enough fat for three days. Flickr photo by jayneandd
You can't go wrong choosing the salad, right? Not quite. Whether you're creating your own or ordering one at a restaurant, beware of piling on too many toppings like bacon, fried chicken, tortilla chips, creamy dressings, croutons, cheese and eggs. IHOP serves a Crispy Chicken Salad that's guilty of many of the above no-nos: It's topped with fried chicken, bacon, two kinds of cheese and a hard-boiled egg, and served with garlic bread, clocking in at 95 grams of fat. Applebee's serves an Oriental Chicken Salad that illustrates another common problem: dressing. Without the vinaigrette, this mix of greens, chicken, almonds and crispy noodles clocks in at 41 grams of fat -- which on its own is nearing the lower end of the suggested daily intake range. But with the dressing? That'll be 99 grams of fat! Flickr photo by manu flickr2010
This American staple can be part of a healthy diet -- when toppings, cooking method and bread type are taken into consideration. But one of the biggest problems with today's burgers is their sheer size. A serving of meat is generally considered to be three ounces, about the size of a deck of cards. You might make an appropriately-sized patty at home to throw on the grill, but when's the last time you saw a three-ounce burger on a restaurant menu? One particularly scary option: Hardee's 2/3-lb. Monster Thickburger. With two 1/3-lb. patties, four strips of bacon, three slices of cheese and mayo, it'll set you back 92 grams of fat -- as much as that stick of butter. Flickr photo by kalleboo
Pizza burgers, quesadilla burgers, burgers that have doughnuts for buns -- our cravings for fatty foods have led us to try all sorts of wacky combinations. But, like salad toppings, burger toppings, especially when they are really piled high, can cause fat counts to suddenly skyrocket. TGIFriday's Southwestern Burger is a serious offender, with cheese, spread, avocado and fried onion strings, rounding this mega-meal out to 100 grams of fat. Flickr photo by Tavallai
You've probably heard that you generally don't want to drink your calories. Well, you probably don't want to drink your fat, either. While shakes and smoothies can be healthy, they are often loaded with hidden sugars and fats. You probably wouldn't expect to find a healthy shake at an ice cream store, but Cold Stone Creamery's PB&C Shake blows regular ice cream out of the water. This indulgent sip has made headlines around the world after Men's Health named it the worst beverage in America. At the time, the chocolate ice cream, milk and peanut butter concoction was listed at 131 grams of fat -- the equivalent of about 68 strips of bacon, Men's Health wrote. Today, Coldstone's website clocks the large size at well over a stick of butter, with 118 grams of fat. (Even the small has an entire day's worth, at 74 grams!) Flickr photo by gemsling
This southern splurge became trendy in late 2009 and has enjoyed a lengthy 15 minutes of fame over the last few years. For the time being, the fried chicken buzz may have settled down, but the dish will remain a standby on comfort-food and southern-style menus. You can healthy up this pick by opting for veggie sides, white meat chicken and by removing the crispy skin. You can also trim back the portions. The Popeye's website depicts a meal consisting of three pieces of chicken, plus a biscuit and a side. We calculated that a similar meal, topped off with a slice of pecan pie for dessert, would add up to 108 grams of fat. Flickr photo by delgaudm
All that ooey-gooey cheese, sour cream and guacamole really add up. Other ingredients, like chicken, may be deep-fried. And tortillas are often coated in butter to get that perfectly-toasted appearance. Of course, portion size is a factor here again. If you're craving a quesadilla, opt for an appetizer-sized one. Ruby Tuesday's Baja Chicken Quesadilla sounds innocent enough -- it's stuffed with grilled peppers and onions, and topped with a chile-lime sauce. But one order costs you 95 grams of fat! Flickr photo by mallydally
The results did not mean people having the occasional unhealthy treat risked damaging their brains, she said.
"The key is to avoid excessive weight gain and to eat sensibly in the first place," she added. "We all deserve a treat now and then."
Another study presented at the meeting showed how the way snacks are presented in cafes can alter people's eating habits.
Pictures of healthy, less healthy, and unhealthy items were arranged in a line beneath the number of calories each contained.
The healthiest foods, such as fruit and cereal bars, were on the left and the unhealthiest, such as chocolate and cake, on the right. A message read: "If you want to consume fewer calories today then choose a snack from the left."
Tested in two coffee shops, the sign led people to reduce the energy value of snacks they bought by about 66 calories on average.
Psychologist Dr Julia Allan, from the University of Aberdeen, said: "We're very excited by this. Research from the US has shown that if you consistently reduce calorie intake by about 100 calories that can lead to weight loss."