A new study found cutting carbs or fats both result in about the same amount of excess weight loss. However, there was a lot of weight loss variability among people for each type of diet, which suggests that what works for some people won’t necessarily work the same way for others.
Christopher Gardner, a professor of medicine at Stanford University, says that every individual’s body is unique, and we’re only beginning to understand the reasons for this diversity.
“We’ve all heard stories of a friend who went on one diet — it worked great — and then another friend tried the same diet, and it didn’t work at all,” Gardner said in a statement.
“Maybe we shouldn’t be asking what’s the best diet, but what’s the best diet for whom?”
He and colleagues investigated the biological nuances that that might encourage a person’s body to favor a low-carb diet over a low-fat diet with weight loss as the main objective.
The team enlisted 609 participants between the ages of 18 and 50. which were divided into two equally-sized groups. One followed a low-carb diet, which started off pretty aggressively as participants were allowed to eat only 20 grams of carbs per day — that’s no more than one a half slices of whole wheat bread. The other group went low-fat, starting with no more than 20 grams of fat per day, the equivalent to a handful of nuts.
After the first month, the participants were instructed to gradually add 5-15 grams of fat or carbs to their diets until they reached a more balanced diet. Studies have shown that if a diet is too aggressive with what and how much people are allowed to it, then rebounds are very likely — the key is to find a balanced nutrition.
Twelve months later, the low-fat diet group reported intaking 57 grams of grams on average while the low-carb group consumed 132 grams of carbohydrates per day. Before the study started, the average fat consumption for the participants was around 87 grams a day, and average carbohydrate intake was about 247 grams.
Before they embarked on the study, each participant had part of their genome sequenced and their baseline insulin outputs measured. This was to allow scientists to investigate any gene patterns that might be associated with weight loss from carb or fat metabolism.
“We made sure to tell everybody, regardless of which diet they were on, to go to the farmer’s market, and don’t buy processed convenience food crap. Also, we advised them to diet in a way that didn’t make them feel hungry or deprived — otherwise it’s hard to maintain the diet in the long run,” said Gardner. “We wanted them to choose a low-fat or low-carb diet plan that they could potentially follow forever, rather than a diet that they’d drop when the study ended.”
By the end of the study, individuals in both groups lost weight, on average about 13 pounds (almost 6kg). However, some dropped as much as 60 pounds (27kg), while others, on the opposite end of the spectrum, gained 15 or 20. This huge variability was observed for both kinds of diets. Perhaps, it could be explained by genotype patterns and baseline insulin levels, but Gardner and colleagues failed to make any association between these factors and the propensity to succeed on either diet.
So, by answering some questions, the research is opening the door to new ones. Gardner and colleagues now want to investigate the microbiome, epigenetics, or a different gene expression pattern they’ve yet to figure out for clues that might explain the drastic variability.
For you the reader, the biggest takeaways would be that there isn’t a clear-cut winner between low-fat and low-carb. It really depends on your body, so if you fail on low-carb, try low-fat, and vice-versa. And regardless of your diet, choose to eat less sugar, less refine flout and as many vegetables as possible.
“On both sides, we heard from people who had lost the most weight that we had helped them change their relationship to food, and that now they were more thoughtful about how they ate,” said Gardner.
“I’m hoping that we can come up with signatures of sorts,” he said. “I feel like we owe it to Americans to be smarter than to just say ‘eat less.’ I still think there is an opportunity to discover some personalization to it — now we just need to work on tying the pieces together.”
The findings appeared in the journal JAMA.