Lisa Lansing

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Carbs vs. fat: it does matter!

This post is a response to the article Carbs vs. fat – which is the real devil? by fellow vegan blogger Tobias Sjösten. He offers the other side of the coin to my post from Monday, Low carb diets never work.

In Low carb diets never work, my argument was that low carb diets aren’t sustainable for the long-term, therefore following them for any purpose is pointless. If your goal is to lose weight in the short-term, a low carb diet might work temporarily, but this weight loss cannot be maintained because avoiding carbs indefinitely is impossible. The moment you revert back to eating carbs, you will most likely overeat on unhealthy carbohydrates (instead of healthy ones) and gain weight in the process. You will always revert back to eating carbs since carbs are your body’s first choice for energy. Your body is more efficient at burning carbs for energy than it is at burning fat or protein. This is how our bodies work naturally.

In this post, I examine Sjösten’s argument. His argument focuses on how viable high carb and low carb diets are as short-term weight loss solutions. He claims it doesn’t matter whether you focus on eating more carbs or more fat, because in the end, only your adherence to the diet matters. You’ll lose weight if you strictly follow any diet plan, regardless of your focus on carbs or fat.

Sjösten cites four studies in his post to support his claim.

In the first study, 10 obese men were fed a low-calorie liquid diet for two weeks. Half were fed a high carb liquid, meaning it contained a higher percentage of carbs compared to protein or fat (70% carbohydrate, 20% protein, 10% fat). The other half were fed the opposite: a high fat liquid (10% carbohydrate, 20% protein, 70% fat). At the end of the two-week period, both groups lost similar amounts of weight.

In the second study, 16 people (13 adults, 3 children) were fed a liquid diet comprised of various percentages of carbohydrate as cerelose (a form of glucose or sugar derived from starch), a constant 15% of energy as protein (as milk protein), and the balance of energy as fat (as corn oil) over a 33-day period. Researchers found “no detectable evidence of significant variation in energy need as a function of percentage fat intake,” meaning the amount of fat they ate didn’t affect the number of calories they needed. Not sure why this is noteworthy because this is common sense. Eating fat or eating carbs doesn’t change how many calories you need day to day.

In the third study, 43 obese adults ate only 1000 calories per day for 6 weeks. Their diet was either high fat (15% of calories coming from carbohydrate, 32% protein, 53% fat), or high carb (45% carbohydrate, 29% protein, 26% fat). BUT the ‘high carb’ diet used in this study isn’t high carb at all since 26% of calories came from fat. In proper HCLF diets, fat does not exceed 10% of daily calories and neither does protein. The results of this study “showed that it was energy intake, not nutrient composition, that determined weight loss.” The participants lost weight, no doubt because their calories were restricted to only 1000 calories per day.

The fourth study started with 160 participants and was supposed to last a year. About half of all participants quit before the year mark. Only 93 of the initial 160 completed the study. Participants followed one of four diets: Atkins (low carb), Zone (macronutrient balanced), Weight Watchers (calorie restriction), and Ornish (high carb). Participants followed the diet at ‘maximum effort’ for 2 months, then followed it as much as they wanted. They self-reported their adherence to the diet. “Each popular diet modestly reduced body weight and several cardiac risk factors at 1 year. Overall dietary adherence rates were low, although increased adherence was associated with greater weight loss and cardiac risk factor reductions for each diet group.”

I’m not sure why this fourth study was included. This study takes place over a longer period of time (a year) but doesn’t give us enough information for an accurate comparison of the four diets. Around half of the participants dropped out of the study and adherence rates were low overall for the remaining participants. So what does this study tell us? Some “modestly reduced body weight” after a year of following a diet as much as they wanted. Half-hearted attempts bring half-hearted results.

The first three studies take place over a short period of time: 2 weeks, 33 days, 6 weeks. So for short-term weight loss, these studies do prove Sjösten’s claim at its most basic level. In some of these studies, people lost weight no matter the macronutrient ratio of their prescribed diet. His claim seems to be correct: it doesn’t matter if you eat high carb or low carb if your only focus is weight loss.

You could follow ANY diet that reduces your calorie intake for a few weeks and lose weight, as long as you stick to it. The reason the participants in the 1st and 3rd studies lost weight is that they were subjected to low-calorie diets. So yes, if you restrict your calories to an unhealthy level (1000 per day), you’ll lose weight regardless of the macronutrient ratio of your food. If your daily calories consisted of 1000 calories of pure oil you’d still lose weight.

But these studies simplify the issue. Sjösten boasts of the objectivity of metabolic ward studies since these take place in a controlled environment, but metabolic wards do not mimic real-life eating. The first and second study used liquid diets. The third may have been liquid as well, but I can’t verify it. A liquid diet does not mimic HCLF eating in the slightest even if the macronutrient ratio of the slurry can be considered HCLF (like 80% carbs, 10% protein, 10% fat). These liquid diets are devoid of fibre, vitamins, and minerals, which are all abundantly present in fruits and vegetables.

Just to keep it balanced, here’s an NIH study from 2015 that found cutting dietary fat reduces body fat more than cutting carbs. This study seems to counter Sjösten’s claim.

In a recent study, restricting dietary fat led to body fat loss at a rate 68 percent higher than cutting the same number of carbohydrate calories when adults with obesity ate strictly controlled diets. Carb restriction lowered production of the fat-regulating hormone insulin and increased fat burning as expected, whereas fat restriction had no observed changes in insulin production or fat burning.

“Compared to the reduced-fat diet, the reduced-carb diet was particularly effective at lowering insulin secretion and increasing fat burning, resulting in significant body fat loss,” said Kevin Hall, Ph.D., NIDDK senior investigator and lead study author. “But interestingly, study participants lost even more body fat during the fat-restricted diet, as it resulted in a greater imbalance between the fat eaten and fat burned. These findings counter the theory that body fat loss necessarily requires decreasing insulin, thereby increasing the release of stored fat from fat tissue and increasing the amount of fat burned by the body.”

The researchers studied 19 non-diabetic men and women with obesity in the Metabolic Clinical Research Unit at the NIH Clinical Center in Bethesda, Maryland. Participants stayed in the unit 24 hours per day for two extended visits, eating the same food and doing the same activities. For the first five days of each visit they ate a baseline balanced diet. Then for six days, they were fed diets containing 30 percent fewer calories, achieved by cutting either only total carbs or total fat from the baseline diet, while eating the same amount of protein. They switched diets during the second visit.

The results of this study show that carbs don’t contribute to weight gain. In fact, they may contribute to more fat burning and more weight loss.

More studies need to be done, but the sad reality is that no one profits from high carb diets. If it is true that high carb diets are objectively better for fat burning, the solution would be that we should eat more fruits and veggies and eat less fat and protein. That means we wouldn’t need to buy protein powders, supplements, and other unnecessary processed food. I don’t expect studies to prove this anytime soon since the weight loss industry and processed food industry both have much to gain from people believing the opposite: that we need something other than real food to solve our weight and health issues.

To achieve optimum health, eat real food like fruits and exercise. It’s that simple.

But I digress: Sjösten’s argument was presented to me as a counter-argument to my argument in Monday’s post, but his argument doesn’t counter mine at all.

His argument focuses on how successful high carb and low carbs diets are for weight loss in the short-term, whereas my argument focuses on how sustainable these diets are in the long-term, not only for weight loss and management but for overall health and wellness. While it’s true that my post on Monday focused on weight loss, weight loss is not the only reason why I promote HCLF as a lifestyle.

None of the results from the studies cited by Sjösten offer any insight regarding the viability of high carb or low carb diet for a lifestyle, meaning eating high carb or low carb for a long period of time, because of the short-term nature of the studies. Even the study I presented doesn’t tell us if high carb would be feasible over a long period of time.

If Sjösten believes a low carb diet works just as well as a high carb diet for the long-term, he would need to provide long-term metabolic ward studies to prove his claim, since metabolic ward studies are the only type of evidence he deems objective and accurate. He would have difficulty proving his claim this way since long-term metabolic ward studies don’t exist. These studies aren’t practical because they are unnatural. Liquid diets of glucose, milk protein, and corn oil do not represent eating in the real world. Neither do 1000 calorie diets.

None of these studies tell us anything about how these diets work in real-life situations, save for the fourth study, which shows us that lack of motivation = lack of results.

The biggest issue I have with Sjösten’s post is that he implies that weight loss = health and wellness, and that simply isn’t true. And even if his claim holds true for long-term weight loss (which it doesn’t, since we don’t have evidence to support that), there are other important reasons why we shouldn’t follow a low carb diet. Just because you can lose weight on a low carb diet doesn’t mean you should follow it!

Deciding to follow a diet solely for the purpose of short-term weight loss is stupid. You can lose weight in many ways, most of them unhealthy and unsustainable. Instead, aim to follow a healthy lifestyle. Not only will weight loss come naturally, but it will also be sustainable for life.

I continue this topic in tomorrow’s blog post: Low carb works, but low fat works better. I’ll argue that the macronutrient ratio of our diets does matter for long-term sustainable weight loss and for optimal health.

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