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.
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.
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 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.
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