Are Low Carbohydrate Diets Best for Weight Loss?

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If you haven’t been bombarded with advertising for low carbohydrate foods, diets, plans and crazed anti-carbohydrate friends and coworkers in the past few years, you must be living on a remote island somewhere (taking any visitors?). The anti-carbohydrate, pro-fat crowd (including keto, Paleo, and Whole 30 – aka Paleo reinvented) devotees might be onto something. But that “something” isn’t a miraculous cure for obesity. Should you trade your low fat, higher carbohydrate diet for full fat foods and “bread” made from cauliflower and mozzarella cheese? It’s time to look past the media headlines to the latest research on low fat vs. low carbohydrate diets.

In this article I’ll cover:

  • the latest research on lower carbohydrate diets;
  • what this research means for you; and
  • a sidenote on the insulin hypothesis.

Should you switch to low carbohydrate vs. high carbohydrate foods?

The Latest Research on Low Carbohydrate Diets

In an attempt to determine which diet is best for weight loss, one of the latest studies collected and analyzed studies on low fat and low carbohydrate diets. A systematic review and meta-analysis, which combines the results of several studies, compared intervention studies > 1 year in length where participants were placed on low fat diets, low carbohydrate diets, other high fat dietary interventions or they continued eating whatever they wanted (their typical diet). Low fat diets ranged from  < 10% of calories from fat to < 30% of calories from fat. The diet interventions used ranged from providing instructions at the start of the study and expecting participants to follow the diet plan to regular counseling sessions with dietitians, food diaries and cooking lessons to actual feeding studies where participants were given most of their overall food intake (with the last approach the most well-controlled). Some studies coached participants to cut calories while others, including those put on low-carbohydrate Atkins-style diets, were told to eat until they were full without worrying about calories.

They analyzed results from 13 trials that examined weight maintenance as well as studies that didn’t include weight loss as a primary goal. In these studies low-fat and high-fat diets lead to a similar amount of weight loss. Low-fat diets were superior only when compared to the subjects’ normal diet – in other words actually going on a diet led to greater weight loss than not dieting (no surprise there). The tiebreaker came from an analysis of 35 weight loss trials, 29 of which were conducted using adults who were overweight, obese, or had type II diabetes. Overall, there was no difference between low-fat and high-fat diet interventions. Low-fat diets led to greater weight loss compared to groups who didn’t diet. However, higher fat diets were the clear winner (according to the headlines), leading to significantly greater weight loss after a year than low fat diets. Before tossing out your steel cut oatmeal, whole-grain bread and fresh Summer fruit, let’s take a closer look at this data. It was pulled from a comparison between low-fat diets and high-fat diets that varied by more than 5% of calories. So did low carbohydrate, higher fat diets really win or was it because subjects cut calories? Is it easier to cut calories on low carbohydrate, high fat diets? Participants on low carbohydrate diets lost about 2.2 pounds more weight after one year versus those on a low-fat diet. A 2.2-pound difference in weight loss after one year on a diet isn’t very impressive, especially considering many of the subjects were overweight or obese to begin with.

The End of Higher Carbohydrate, Low-Fat Diets?

Based on these results the authors suggest low-fat diets shouldn’t be the go-to recommendation for weight loss. However, the results of this study are mainly applicable to overweight, obese and type II diabetics – the primary populations examined in these studies. We can’t take the authors conclusion that low carbohydrate, higher fat diets are better if you are looking to lose a few pounds for a beach ready body. What works for an obese adult or type II diabetic will not necessarily work for an active adult who wants to get a 6-pack. Secondly, previous research shows low carbohydrate diets tend to produce greater weight loss, initially, than low fat diets (some of this is water weight since carbohydrates store 3-4 times their weight in water in the form of glycogen in muscles and the liver and your glycogen stores will start dropping when you drastically lower your carbohydrate intake) yet after a year, weight loss is equivalent between both diets. Other research shows weight loss over the first six months on a diet is the main predictor of both weight loss success and sticking to a diet over the long-term. Greater weight loss initially = better adherence = better success over time.

Long-term Success

What’s more disappointing than the paltry 2.2-pound difference between the low-fat and high-fat diets after one year is the total average weight loss in the studies designed for weight loss – a mere 8.25 lbs. after 1 year. Instead of declaring low carbohydrate, higher fat diets a clear winner over low fat, higher carbohydrate diets (especially considering the 2.2 pound difference), we should be asking why it’s tough to stay on a diet, any diet? Why aren’t study participants losing more weight? I don’t have the answer to these questions and leading weight loss researchers don’t seem to have a complete picture right now either.

If you want to lose weight, choose a lower calorie diet primarily based on high quality foods or create your own plan that fits into your lifestyle and is one you can stick with it. There are many diets that could, potentially, work for you. If you want to try a low carbohydrate diet for a while, by all means go for it (especially if you need to see that number on the scale move pretty quickly)! If cutting carbs sounds like being in detention, then skip that approach! I’m giving you permission to alter your plan as often as you need to based on changes in your lifestyle (some research papers actually suggest doing this and I am a huge fan of this approach), motivation, and results.

Conceptually, low carbohydrate diets are very easy. You don’t have to worry about portion sizes, log calories, count points or determine if you have to eat less at dinner to make up for a lunchtime splurge. Decision-making is boiled down to: it contains carbs and therefore off my diet or it is low in carbs and the carbs it does contain are high in fiber so I can eat it. Just don’t buy into the hype that low fat, higher carbohydrate diets are the only way to lose weight or that these diets are better, over the long term, than other dietary approaches that also cut calories.

References

Tobias DK, Chen M, Manson JE, Ludwig DS, Willett W, Hu FB. Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis. Lancet Epub before print. 29 October 2015.

Greenberg I, Stampfer MJ, Schwarzfuchs D, Shai I; DIRECT Group. Adherence and success in long-term weight loss diets: the dietary intervention randomized controlled trial (DIRECT). J Am Coll Nutr 2009;28(2):159-68.

Franz MJ, VanWormer JJ, Crain AL, Boucher JL, Histon T, Caplan W, Bowman JD, Pronk NP. Weight-loss outcomes: a systematic review and meta-analysis of weight-loss clinical trials with a minimum 1-year follow-up. J Am Diet Assoc 2007;107(10):1755-67.

Hall KD. Predicting metabolic adaptation, body weight change, and energy intake in humans. Am J Physiol Endocrinol Metab 2010;298(3):E449-66.

Hall KD, Sacks G, Chandramohan D, Chow CC, Wang YC, Gortmaker SL, Swinburn BA. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011; 378(9793).

Rosqvist F, Iggman D, Kullberg J, Cedernaes J, Johansson HE, Larsson A, Johansson L6, Ahlström H, Arner P, Dahlman I, Risérus U. Overfeeding polyunsaturated and saturated fat causes distinct effects on liver and visceral fat accumulation in humans. Diabetes 2014;63(7):2356-68.

 

 

 

Do Carbohydrates Make You Fat?

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When I was in college I would often eat 3-4 bagels per day (free from the cafeteria and portable), along with cream of wheat in the morning, fruit and/or starchy veggies at lunch, heaping quantities of brown rice at dinner, and a bowl (or two) of Raisin Bran with milk after dinner. I wasn’t on an all carbohydrate diet, I ate all of this in addition to regular meals . As a cross country runner, I was just plain hungry. Despite my high carb diet, my body fat via underwater weighing (the benefit of being an exercise physiology student) was very low, as in elite distance runner low. So when I hear people suggest carbohydrates are a surefire path to obesity for everyone, I shake my head and think “no, clearly they are not.”

Carbohydrates have taken a hit in recent years because 1) they taste good and are therefore easy to overeat (Which one tastes better: a jumbo size blueberry muffin or grilled chicken breast?) and 2) carbohydrates stimulate the release of insulin from our pancreas, a hormone that increases carbohydrate (in the form of sugar) uptake by muscle and fat cells while also suppressing the breakdown of fat tissue. Sounds like a double whammy right? It definitely can be if you chronically overeat. But, if you only eat the amount of calories you need each day or less than you need over time, you’ll maintain or even lose weight (in the absence of Type 2 diabetes or insulin resistance). And that is why the weight loss research shows that over time higher carbohydrate diets result in similar weight loss as low carbohydrate diets in healthy individuals. However, there are two big caveats to this “total calories” approach to weight loss:

1) If you don’t eat enough protein each day (and I recommend a minimum of 30 grams of protein at breakfast, lunch and dinner) – 0.55 – 0.91 grams per pound of body weight per day, you will lose a good bit of muscle during weight loss.

2) If you have insulin resistance, PCOS or Type 2 diabetes, a lower carbohydrate diet combined with exercise is the most effective way to take off weight (work with your MD to adjust any glucose lowering medications or insulin you are on based on your change in diet and/or drop in weight).

If you want to read more on this topic including the design of an exciting upcoming study, check out this thorough overview I wrote for FitnessRx.

In the meantime, remember there is no one perfect diet for all people. Are there times I ask my clients to cut down on their intake of carbs (particularly the junk food carbs)? Yes, absolutely. But, I take their overall diet, goals and what they will realistically do into account. And you should too. Because adherence, the ability to stick with a diet program, is the biggest factor that will predict weight loss success. So don’t jump on your neighbor’s diet detox 2 shakes-per-day bandwagon or let yourself be dragged to Weight Watchers meetings while kicking and screaming.  Instead, take into account your current food intake (what do you like to eat?), lifestyle, cooking skills, medical history, diet history and physical activity and come up with a plan that works for you.