Do Carbs Make You Fat?
When it comes to fat loss dieting, reducing carbohydrates, specifically refined sugar and starches, can be very effective in reducing calories from our daily allowance without missing out on essential nutrients. Espeically when intake of fruits and vegetables are encouraged as part of the routine, dieters can achieve a substantial amount of energy deficit while maintain good health and fitness.
As simple as that sounds, dieters and gurus alike always find ways to take a working formula and modify it to the extreme for the sake of faster results. Their mindset is always, “If something works, then more is better!”. While I am a major supporter of reducing excessive carbohydrates, popular Low Carb Diets (LCDs) such as the Protein Power Diet, Aktins’ New Diet Revolution, and The South Beach Diet are still commiting to the “more is better” philosophy.
With marketing in mind, popular diets are typically way simplified (dumbed down) where they completely dismiss the scientific evidence originally claimed to be the working foundation of its setup. In most cases, it’s about giving the diet a “hook” that can be easily understood and convincible enough to give dieters a go. In life, nothing is ever that simple.
Today, I’d like to address the methodologies low-carbers love to propagate in the mainstream media and explain why they are not always as effective or superior than other diets. I will use the Atkins Diet as a leading example to demostrate common false premises within LCDs. Before I delve into the research, I must make a disclaimer that this article is not meant to discourage dieters from following LCDs, specifically. I simply want readers to have a clear understanding of why low carbing should be context specific with sound physiological principles working in their favor.
Atkins’ New Revolution Diet
Atkins and his team targeted carbohydrates as the enemy of our nation’s obesity epidemic. Many of their original approaches showed promising results in the clinical field such as alievating symptoms of type II diabetes 1, 2, 3, epilepsy, parkinson’s, alzheimer’s, hypercholesterolemia, hypertriglyceridemia, and cancer but the research on obesity (compared to balanced, calorie-restriction diets) is still debatable and lacking in long-term studies.
One of their most nutorious claims is that carb restriction (independent of calorie restriction) offers the human body a “metabolic advantage” for regulating fat metabolism. This ideal metabolic environment supports optimal health and leanness. Some extreme LC alarmists have even advised dieters to limit their fruit intake due to its fructose (fruit sugar) content. Other popular LCDs typically offer unlimited amount of fat intake (except South Beach) while carbs are limited to under 100g/day. Total average calories does not matter and exercise ‘may’ help but is not required to achieve fat loss.
In the LC world, it’s not how many calories they consume or how little energy they expend. It’s about two things: insulin and carbohydrates. Atkins and his followers believe that the primary cause of excess body fat accumulation is the result of carb intake and hyperinsulinemia. Basically, the theory goes like this: 1) insulin correlates positively with carbs, 2) insulin is the only hormone that drives fat storage, 3) by restricting intakes of carbs, we can prevent the insulin response, and 4) since we all need to eat something, we should get our calories from a higher intake of fat and protein.
That’s the ‘hook’ as most low-carbers knows it and I wish human physiology were only that simple…
The Metabolic Advantage Theory Debunked
Low-Carb Myth #1: Insulin is the main driver for energy storage (fat synthesis) and is largely affected by carb intake.
While it is true that insulin does helps store calories into our fat cells, it is not the only one. The most common mistake low-carbers make when they hit a fat loss stall is eating too much fat due to its neutral relationship with insulin.
Dietary fat and serum fatty acids can be repackaged and stored back into our fat cells via acylation-stimulating-protein (ASP) 1, 2, 3. ASP is produced by our adipocytes (fat cells) to serve as a plasma triglyceride clearance hormone removing excess lipids from our blood into our fat cells. This hormone is more potent at fat synthesis than insulin and can even augment insulin secretion.
This metabolic pathway requires no carbs to be ingested (independent of insulin) and is very efficient at keeping calories inside fat cells 1, 2, 3. In fact, dietary fat is the least energy taxing nutrient for fat storage compared to other macronutrients.
Low-Carb Myth #2: Calories from carbs are easily stored as fat in the presence of insulin.
False. The efficacy of synthesizing fat from carbs (via de novo lipogenesis) is very poor to almost non-existent. What actually occur is that when carbs are consumed, fat cells stop (but not always) releasing fatty acids to be burned as fuel while the body switches to (carbohydrates-derived) glucose metabolism. Like alcohol, carb metabolism precedes fat metabolism.
Chroinc elevations of insulin under hypercaloric conditions can be fattening while overfeeding carbs under hypocaloric conditions cannot. By looking at the bigger picture, the calories we stored from carbs (or anything else for that matter) get released for oxidation (burned) in the fasted state (between meals and sleep). For fat gain to occur, we have to chronically take in more calories than our daily energy output. In this case, food composition does not matter.
Low-Carb Myth #3: Carb ingestion elicits insulin spikes while dietary fat and protein do not.
False. Some protein sources are just as insulinemic as carbs regardless of their glycemic load.
Research: “An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods” by SH, Holt
“Significant differences in insulin score were found both within and among the food categories and also among foods containing a similar amount of carbohydrate. Overall, glucose and insulin scores were highly correlated (r = 0.70, P < 0.001, n = 38). However, protein-rich foods and bakery products (rich in fat and refined carbohydrate) elicited insulin responses that were disproportionately higher than their glycemic responses”
If dieters only knew of insulin as the only hormone that signals fat storage while having just learned protein is just as insulinemic, low-carbers would have to eat pure fat (sticks of butter) to avoid fat gain. In this case, they would also have to ignorantly dismiss the ASP mechanism mentioned earlier as well.
Low-Carb Myth #4: Low blood sugar due to insulin spikes make us hungry faster and slow our metabolism.
Low-Carb Myth #5: We can prevent insulin spikes by reducing carbs and choosing lower glycemic index (GI) foods.
Research: A systematic review was done on 31 studies comparing high and low GI diets concluded that neither high GI nor hyperinsulinmia drives us to eat more or burn less calories.
“Should obese patients be counselled to follow a low-glycaemic index diet? No” A. Raben
“A systematic review was performed of published human intervention studies comparing the effects of high- and low-GI foods or diets on appetite, food intake, energy expenditure and body weight. In a total of 31 short-term studies (<1 d), low-GI foods were associated with greater satiety or reduced hunger in 15 studies, whereas reduced satiety or no differences were seen in 16 other studies. Low-GI foods reduced ad libitum food intake in seven studies, but not in eight other studies. In 20 longer-term studies (<6 months), a weight loss on a low-GI diet was seen in four and on a high-GI diet in two, with no difference recorded in 14. The average weight loss was 1.5 kg on a low-GI diet and 1.6 kg on a high-GI diet. To conclude, there is no evidence at present that low-GI foods are superior to high-GI foods in regard to long-term body weight control.”
GI and insulin’s overall effect on appetite and energy intake is still unclear in current research literatures. The GI scale does not proportionally correlate with insulin responses but can be generally helpful for diabetics when applied meticulously. Dieters who may be insulin resistant, having a low amount of carbs along with plenty fat and protein in each meal should be sufficient in stabilizing their insulin. In any case, the quantity of carbs outweights the quality (GI) of carbs when it comes to managing blood glucose levels.
For strictly fat loss, healthy dieters who are entirely responsible for making their own food choices can safely ignore the GI and just try to eat complex/fibrous carbs in general. This will save them a lot of time and energy. On a quick sidenote, high GI foods can be helpful for athletes in replenishing glycogen storage and optimizing recovery.
Low-Carb Myth #6: Insulin and carbohydrates are the cause of obesity.
High-carb diets gave subjects similiar weight loss compared to low-carb diets when calorie intake is below one’s maintenance.
Research: Obesity Treatment: Can Diet Composition Play a Role? James O. Hill
“During weight reduction, the extent of negative energy balance is the greatest determinant of the amount and rate of weight loss, and any effects of diet composition are likely to be very small”
In another study by Golay et al., randomly assigned 43 adult, obese persons to a 1000kcal/d diet composed of either 15% carbohydrates or 45% carbohydrate diet. All subjects lost body fat and decreased waist-to-hip ratio, but no significant difference was observed in either group. “The result of this study showed that it was energy intake, not nutrient composition, that determined weight loss…”
If you’re following Aktins or any other LCDs, do not foolishly eat as much fat as you want and not expect to gain or not lose any weight. If you are actually at a negetive energy balance, carb intake, insulin sensitivity, and GI generally won’t matter much. When it comes to losing weight, calorie reduction alone (relative to daily expenditure) ultimately dictates the success of weight loss.
1. In the absence of insulin, fat synthesis is just as easily achievable via ASP.
2. Carbohyrate metabolism precedes fat metabolism and carbs are rarely stored as body fat (at least not in humans).
3. Dietary proteins can be just as insulinemic as carbs.
4. Insulin does not necessarily make us hungrier or lazier.
5. The GI scale is not always effective in predicting insulin response, satiety, and metabolic rate. It can be somewhat helpful for diabetics (secondary to the amount of carbs consumed) under intense scrutiny and application.
6. Sugar/carbs/insulin alone will not make people fat nor prevent weight gain. Eating too much and moving too little, relative to our average metabolic rate will.
A commonly used phrase in the LC community is “A calorie is not just a calorie“. Other than the “metabolic advantage” myths proposed above, there is some truth to that saying. For example, higher protein intake can promote thermogenesis, longer satiety, exercise recovery, while fibrous carbs (but not always low GI) can keep us full longer and prevent overeating. Nevertheless, calorie reduction (quantity control) is the key and the law to losing weight.
LCDs are not magic and generally won’t support most endurance sports or strength training. Those who are active and have no metabolic defects will generally fare better on a balanced, caloric-reduction diet or a targeted/cyclical LCD for fat loss.
Overeating (esp. with fat intake) among LC dieters occur rampantly when calorie counting and portion control are not addressed. To simply assume a low carb diet is equivalent to a calorie-reduction diet is misleading. The bottom line is, If you want to lose weight, the output of energy has to exceed the input long enough to see results.
Elements Challenging the Glycemic Index By Alan Aragon
Low Carb Dogma By Jamie Hale
Lyle McDonald Interview Part 3 (Carbohydrates) by Body Improvements