Food and nutrition security among rural and peri-urban households in Sub-Saharan Africa remains precarious, particularly under conditions of stress driven by seasonal scarcity, income volatility, and climate impacts. Existing literature highlights the importance of gendered roles in food provisioning, income control, and caregiving in shaping household food priorities, yet less is known about how gendered decision-making dynamics shift under stress and how these dynamics mediate dietary coping strategies. This study addresses this gap by examining two core questions: (1) what dietary coping strategies households employ in response to stress, and (2) how these dietary adjustments are mediated through gendered decision-making within households. The study presents and analyses data from a novel Participatory Food Budgeting and Negotiation (PaFBaN) method, alongside food purchasing and preparation observations, conducted in two contrasting contexts: rural Malawi and peri-urban Zambia. Across both contexts, findings reveal strikingly consistent dietary outcomes under stress. Households defaulted to carbohydrate-based staples—most notably maize—supplemented by inexpensive vegetables and minimal protein. This convergence reflects constraint-driven adaptation, where affordability, caloric sufficiency, and availability dominate food choices rather than preference or nutrition and food safety concerns. There were very small differences between men’s and women’s budgets in both cases. Negotiated lean budgets were more similar to women’s than men’s suggesting women’s greater agency in this context., women played a central role in negotiating food budgets, drawing on their detailed knowledge of prices, portions, and meal preparation to correct men’s cost and quantity estimates, altering the composition and accuracy of the food budgets to some extent. Men’s influence increased as available resources increase and households incorporate discretionary, status-linked, or identity-related foods, while women continued to prioritise dietary adequacy, continuity, and meal management. The study reframes gendered dietary behaviour under chronic stress as negotiated adaptation, underscoring the need for food security interventions and consumer education that address both material scarcity and intra-household decision regimes.