Wednesday I explained why "butter is back" is not useful dietary advice, even when studies show that eating butter has little or no effect on disease risk (the total diet and calories are what matter). Now I can say the same thing about low-carbohydrate diets.
The debate about whether fat or carbohydrates is responsible for obesity has passionate advocates on both sides, although those for carbohydrates predominate in the press these days.
The main scientific model behind the low-carb approach is the "carbohydrate-insulin hypothesis," which journalist Gary Taubes, Harvard professor David Ludwig and others have extensively promoted. It suggests that a diet heavy in carbohydrates (especially refined grains and sugars) leads to weight gain because of a specific mechanism: Carbs drive up insulin in the body, causing the body to hold on to fat and suppress calorie burn.
According to this hypothesis, to lose weight you reduce the amount of carb calories you eat and replace them with fat calories. This is supposed to drive down insulin levels, boost calorie burn and help fat melt away … instead of just cutting calories, you're supposed to change the kinds of calories in your diet to lose weight.
To his great credit, Gary Taubes was willing to put this hypothesis to the test. He organized the Nutrition Science Initiative (NuSI) to fund studies that he must have hoped would demonstrate the benefits of low-carb diets.
To its great credit, NuSI recruited highly experienced and respected obesity investigators to design and conduct the studies.
The first of these studies has just been published. It fully discloses the role of NuSI.
Supported by the Nutrition Sciences Initiative … Nutrition Sciences Initiative (NuSI) convened the research team, helped formulate the hypothesis and provided partial funding. NuSI and its scientific advisors were given the opportunity to comment on the study design and the manuscript, but the investigators retained full editorial control.
In this case, because I am familiar with the work of some of the investigators, I'm inclined to take these statements at face value.
Here's what they did. They put 17 overweight or obese men in a metabolic ward and fed them a very low carbohydrate diet, so low that it would induce fat breakdown and ketosis. The calories were supposed to be sufficient to maintain weight, but were not. The men lost weight from water excretion and breakdown of body protein as well as of fat, as is typical of what happens during partial starvation. Energy expenditure did not increase to the level anticipated from the carbohydrate-insulin model.
The abstract concluded:
The isocaloric KD [ketogenic, very low carbohydrate diet] was not accompanied by increased body fat loss but was associated with relatively small increases in EE [energy expenditure] that were near the limits of detection [translation: barely detectable] with the use of state-of-the-art technology.
The discussion concluded:
Therefore, our data do not support the carbohydrate–insulin model predictions of physiologically relevant increases in EE or greater body fat loss in response to an isocaloric KD. However, it is possible that dietary carbohydrate restriction might result in decreased ad libitum energy intake—a prediction of the carbohydrate-insulin model that was not tested in the current study but deserves further investigation.
In other words, restricting carbohydrate does not increase body fat loss or energy expenditure but might help you eat fewer calories.
This result confirms some of the results of a previous study from the first NuSI author. That one, funded by NIH, concluded:
Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to 89 ± 6 g/day of fat loss and was significantly greater than carbohydrate restriction (p = 0.002).
Taken together, these studies show that both low-carbohydrate and low-fat diets cause weight loss when calories are restricted, but low-fat diets cause greater losses in body fat content than do low-carbohydrate diets.
In my book with Malden Nesheim, Why Calories Count: From Science to Politics, we review a 1964 study that put obese patients in a metabolic ward and fed them low-calorie diets of widely varied composition. They lost weight at the same rate on diets ranging from 3 percent to 60 percent carbohydrate and from 13 percent to 83 percent fat. They titled the study Calories Do Count. The NuSI studies confirm the benefits of reducing calories from any source to lose weight.
- With regard to weight loss, calories count and the relative proportions of fat, protein and carbohydrate do not matter much (although low-carb diets may help with eating less).
- With regard to health, the food sources of calories matter very much indeed and nearly everyone would be better off eating less sugar—at the very least because sugars provide calories, but no nutrients.
EcoWatch Daily Newsletter
By Franziska Spritzler
Many people associate the term "low-fat" with health or healthy foods. Some nutritious foods, such as fruits and vegetables, are naturally low in fat.
Low-fat muffins are high in sugar and have a high glycemic index that may lead to hunger, overeating and weight gain.
Here are 10 low-fat foods that are bad for you:
1. Low-Fat Sweetened Breakfast Cereal
In some ways, breakfast cereal appears to be a healthy way to start your day.
For example, it's low in fat and fortified with vitamins and minerals. The packaging also lists health claims such as "contains whole grains."
However, most cereals are loaded with sugar. In the ingredients section, sugar is usually the second or third item listed, meaning it's present in large amounts.
In fact, a 2014 report by the Environmental Working Group found that the average cold breakfast cereal contains nearly 25 percent sugar by weight.
Excess amounts of fructose have been linked to an increased risk of obesity, heart disease, kidney disease, type 2 diabetes and other health problems (1).
Additionally, the "healthiest" low-fat cereals may be some of the worst offenders.
Bottom Line: Low-fat, sweetened breakfast cereals are high in sugar, including "healthy" varieties such as granola.
2. Low-Fat Flavored Coffee Drinks
Coffee is one of the healthiest beverages you can drink.
On the other hand, the high sugar content of flavored low-fat coffee drinks can negatively affect health.
For example, a 16-oz (450-gram) nonfat mocha drink has only 2 grams of fat but a whopping 33 grams of sugar. That's 57 percent of total calories (7).
Not only does this beverage provide a hefty serving of fructose, but it's in liquid form, which seems to be especially harmful to health (8).
Bottom Line: Adding sugar to coffee transforms a healthy beverage into one that may lead to weight gain and disease.
3. Low-Fat Flavored Yogurt
Yogurt has a long-standing reputation as a healthy food.
However, low-fat, sugar-sweetened yogurt contains too much sugar to qualify as a nutritious choice.
In fact, many types of low-fat and nonfat yogurt are as high in sugar as desserts.
For example, 8 ounces (240 grams) of fruit-flavored, nonfat yogurt contains 47 grams of sugar, which is nearly 12 teaspoons. In comparison, an equivalent serving of chocolate pudding has 38 grams of sugar (12, 13).
Bottom Line: Plain yogurt made from whole milk is healthy, but sweetened low-fat yogurt can be as high in sugar as desserts.
4. Low-Fat Salad Dressing
Salad dressing enhances the flavor of raw vegetables and may improve a salad's nutritional value.
Traditional salad dressings are high in fat, which helps your body absorb the fat-soluble vitamins A, D, E and K.
In contrast, low-fat and fat-free salad dressings don't contribute any health benefits to your meal.
Most of them also contain sugar and preservatives.
While it's no surprise that sweet dressings such as honey mustard and Thousand Island are high in sugar, many others are also loaded with sugar or high-fructose corn syrup. This includes fat-free Italian dressing.
Bottom Line: Low-fat and fat-free salad dressings contain sugar and additives but lack the benefits of healthy fats like olive oil.
5. Reduced-Fat Peanut Butter
Peanut butter is a delicious and popular food.
It's high in monounsaturated fat, including oleic acid, which may be responsible for many of the benefits.
However, note that natural peanut butter contains only peanuts and perhaps salt.
By contrast, reduced-fat peanut butter contains sugar and high-fructose corn syrup.
What's more, although the total fat has been reduced from 16 grams to 12, some of the healthy monounsaturated fat has been replaced by processed vegetable oil.
The calorie content of natural peanut butter and reduced-fat peanut butter is the same: 190 calories in 2 tablespoons. However, natural peanut butter is far healthier.
Bottom Line: Reduced-fat peanut butter contains sugars and processed oils yet provides the same number of calories as natural peanut butter, which is much healthier.
6. Low-Fat Muffins
Low-fat muffins may seem like a healthier option than other baked goods, but they're really not any better.
However, this is a much smaller muffin than you'd find in a coffee shop or convenience store.
One group of researchers reported that the average commercial muffin is more than 300 percent larger than the U.S. Department of Agriculture standard size (26).
With the exception of bran muffins, low-fat muffins contain little fiber and often have a high glycemic index (GI). High-GI foods raise blood sugar quickly, which may increase the hunger that drives overeating and leads to weight gain (27).
Bottom Line: Low-fat muffins are high in sugar and have a high glycemic index that may lead to hunger, overeating and weight gain.
7. Low-Fat Frozen Yogurt
Low-fat or nonfat frozen yogurt is considered a healthier choice than ice cream because it's much lower in fat.
However, it contains just as much sugar as ice cream, if not more.
What's more, portion sizes for frozen yogurt are typically much larger than those for ice cream.
Bottom Line: Frozen yogurt contains as much or more sugar than ice cream and it's typically consumed in larger quantities.
8. Low-Fat Cookies
Low-fat cookies aren't any healthier than other cookies. They're also not as tasty.
When the low-fat trend was at its peak in the 1990s, many low-fat cookies filled grocery store shelves.
However, researchers found that these low-fat versions were not very satisfying compared to the originals (30).
Like most low-fat foods, the sugar content of these cookies is high. A fat-free oatmeal raisin cookie has 15 grams of sugar, which is 55 percent of its total calorie content (31).
In addition, low-fat cookies are typically made with refined flour, which is unhealthy.
Bottom Line: Low-fat and fat-free cookies aren't any healthier than regular cookies. They're very high in sugar and also taste worse.
9. Low-Fat Cereal Bars
Low-fat cereal bars are marketed as a healthy on-the-go snack for busy people.
In reality, they're loaded with sugar and contain very little protein, a nutrient that promotes fullness.
In fact, research shows that consuming high-protein snacks can help prevent overeating (32).
One popular low-fat, strawberry-flavored cereal bar contains 13 grams of sugar but only 1 gram of fiber and 2 grams of protein (33).
Bottom Line: Low-fat cereal bars are high in sugar but low in fiber and protein. In addition, they contain far more sugar than fruit.
10. Low-Fat Sandwich Spreads
Low-fat spreads such as margarine aren't a smart choice.
Even though they have less fat than original spreads such as butter, they still contain highly processed vegetable oils that can be harmful to health.
What's more, some of the light spreads specifically marketed as being "heart-healthy" actually contain small amounts of trans fats, which have been linked to inflammation, heart disease and obesity (34, 35, 36).
It's actually much healthier to use modest amounts of butter or healthy mayo rather than processed low-fat spreads.
Bottom Line: Low-fat margarine and spreads are highly processed. They are made with unhealthy vegetable oils and often contain trans fats.
Take Home Message
Low-fat foods may seem healthy, but they're often loaded with sugar and other unhealthy ingredients. These can lead to excessive hunger, weight gain and disease.
For optimal health, it's best to consume unprocessed, whole foods. This includes foods that arenaturally low in fat, as well as foods that naturally contain healthy fats.
This article was reposted from our media associate Authority Nutrition.
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