Understand why you gained and your friend lost on the same eating plan

By Cynthia Sass

The other day a perplexed client asked, "Why is it my wife and I both went vegan, and while she lost weight, I didn't?" Throughout my years in private practice, I've been asked questions like this one numerous times. One person may go vegetarian, vegan, raw, or gluten-free and drop pounds, while a friend, co-worker, or significant other takes the same path and gains weight.

It's confusing, but there's always an explanation, and it typically boils down to how the change impacted each individual's overall nutritional balance. In some cases a diet can bring you back into balance, or at least closer to it, which usually leads to positive outcomes. But a diet can also throw your body further out of whack, leading to added pounds or other unwanted side effects. Here are a few examples:


I'm a big supporter of vegan diets when they're done correctly, but when they're not, they can backfire. If you cut out meat and dairy and fail to replace the protein, you may wind up eating way more carbs than your body can burn or use-and gain weight. In addition, a lack of protein and nutrients can lead to chronic fatigue and muscle loss, which further suppresses metabolism. On the flip side, transitioning from a typical American diet (few fruits and veggies, way too much fatty animal protein, and lots of sugar and refined grains) to a healthy vegan plan (lots of produce, whole grains, lentils, beans, and nuts) can restore balance and fill nutrient gaps, leading to weight loss, soaring energy, and better health.


Dropping a size after giving up gluten often depends on how you were eating before and what your gluten-free diet looks like. If your pre-gluten-free diet was high in refined carbs and sugar and low in protein, and by making the switch you cut out white rice and pasta, baked goods, and beer in favor of more veggies, lean protein, and gluten-free whole grains such as quinoa and wild rice, you'll likely lose weight and feel better than ever. But I've also seen people trade in processed foods containing gluten for gluten-free versions of cookies, chips, candy, and yes, beer, which resulted in no difference on the scale. Note: If you have Celiac disease or are gluten-intolerant, that's another issue. Please check out my previous post about these conditions.


I once had a client who spent a lot of time and money going raw in the hopes of losing weight-instead she gained. After the transition, she downed handfuls of nuts; sipped juices and smoothies loaded with fruit; readily enjoyed desserts and snacks made with dates, coconut and raw chocolate; and ate daily meals with sauces and mock cheeses created from pureed seeds. In her particular case, going raw resulted in feeding her body far more than it needed to get to and stay at her ideal weight, something she wasn't paying attention to.

Bottom line: A diet philosophy alone isn't enough to ensure results. In many ways your body is like a magnificent construction site: There's a blueprint that determines the type and amount of raw materials needed to build and maintain your structure (e.g. carbs, protein, fat, vitamins, minerals, etc.). Let's say you decided to build a sustainable house. Eco-friendly would be the philosophy, but you couldn't throw the conventional blueprint away-you'd still need specific amounts of various supplies to ensure a sound building. When that building is your body, while it is possible to obtain all the nutrients you need on a vegan, gluten-free, or raw diet, achieving that balance is ultimately what will allow you to lose weight and optimize your health.

What's your take on this topic? Has a diet change ever backfired on you? Do you try to keep balance in mind when planning and choosing your meals, regardless of your diet philosophy? Please tweet your thoughts to @cynthiasass and @Shape_Magazine

Cynthia Sass is a registered dietitian with master's degrees in both nutrition science and public health. Frequently seen on national TV, she's a SHAPE contributing editor and nutrition consultant to the New York Rangers and Tampa Bay Rays. Her latest New York Times best seller is S.A.S.S! Yourself Slim: Conquer Cravings, Drop Pounds and Lose Inches.

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January 17, 2018
Wow, that's a fantastic way to put this. I found this out for myself over the many years I've done different ways of eating. At first, I thought I was being a yoyo dieter. But since my diets usually consisted of what seemed like good ideas that are well thought out, I realized finally I was experimenting. I've found out some really important information in all my ups and downs with my body size. I'm on another one now, am really enjoying getting to reconnect with body through this process.